Trouble with manager after introducing htaccess

<div id="modx-leftbar" class=" x-plain" ...>
 <div class="x-plain-bwrap" id="ext-gen12">
  <div class="x-plain-body x-plain-body-noheader" id="ext-gen13" ...>
   <div id="modx-leftbar-tabpanel" class=" x-tab-panel modx-tabs x-tab-panel-noborder" ...>
    <div class="x-tab-panel-header x-tab-panel-header-noborder x-unselectable x-tab-panel-header-plain" id="ext-gen21" ...>
     <div class="x-tab-strip-wrap" id="ext-gen-24" ...>
      <div class="x-tab-strip x-tab-strip-top" id="ext-gen26">
       ...the tabs and info...

<div id="modx-panel-welcome-div">
 <div id="modx-panel-welcome" class=" modx-formpanel container">
  <div class="modx-formpanel-bwrap" id="ext-gen13">
   <div class="modx-formpanel-body modx-formpanel-body-noheader" id="ext-gen14">
    <div id="modx-welcome-header class=" x-panel modx-page-header x-panel-noborder" ...>
     <div class="x-panel-bwrap" id="ext-gen16">
      <div class="x-panel-body x-panel-body-noheader x-panel-body-noborder" id="ext-gen17" ...>
       <h2>undefined</h2>

RewriteRule ^(assets|backups|mgr) - [L,QSA,NC]

# MODX supports Friendly URLs via this .htaccess file. Pages must be
# served via Apache with mod_rewrite to use this functionality. The base
# directory is the root of the site. Note that FollowSymlinks may be
# redundant (it is usually set within httpd.conf), and that the RewriteBase
# must be set to the site root (as "/mainsite" or "/mainsite/").

Options +FollowSymlinks
RewriteEngine On
RewriteBase /mainsite/
RewriteCond %{HTTP_HOST} .
 

# Server should have timezone setting set; if it is not, various issues will arise.
# The following entry can compensate for this; see the details of timezone
# definitions at http://php.net/manual/en/timezones.php.

php_value date.timezone America/Los_Angeles


# Exclude /assets, /backups and /mgr directories from rewrite rules.

##RewriteRule ^(assets|backups|mgr) - [L,QSA,NC]
 

# Make URLs case-insensitive.

RewriteRule ^(.*)$ index.php?q=$1 [L,QSA,NC]


# To allow for both www.site.com and site.com to resolve to site root (for SEO),
# uncomment one of the following options (not both). Note that the R=302 redirect
# should be set to R=301 in the final production site.

# Option (a) is rewrite www.domain.com -> domain.com -- used with SEO Strict URLs plugin
## RewriteCond %{HTTP_HOST} !^mainsite\.com [NC]
## RewriteRule (.*) http://mainsite.com/$1 [R=302,L]
#
# Option (b) is rewrite domain.com -> www.domain.com
RewriteCond %{HTTP_HOST} !^www\.mainsite\.com [NC]
RewriteRule (.*) http://www.mainsite.com/$1 [R=302,L]


# The actual Friendly URLs part; if case-sensitive URLs are preferred, remove the NC.

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?q=$1 [L,QSA,NC]


# The following directives address screen flicker on CSS rollovers.
# The Expires lines (the first four) cause image files to persist in a browser’s
# cache for 30 days (2592000 seconds); for these, be sure that the expires_module
# has been included in the Apache configuration. The remaining four lines actually
# address the flicker issue in specific browsers.

ExpiresActive On
ExpiresByType image/gif A2592000
ExpiresByType image/jpeg A2592000
ExpiresByType image/png A2592000
BrowserMatch "MSIE" brokenvary=1
BrowserMatch "Mozilla/4.[0-9]{2}" brokenvary=1
BrowserMatch "Opera" !brokenvary
SetEnvIf brokenvary 1 force-no-vary 


# Servers that support output compression may be able to realize a
# boost in speed by uncommenting the following lines.

## php_flag zlib.output_compression On
## php_value zlib.output_compression_level 5


# Fix Apache internal dummy connections from breaking the [(site_url)] cache.

## RewriteCond %{HTTP_USER_AGENT} ^.*internal\ dummy\ connection.*$ [NC]
## RewriteRule .* - [F,L]
 

# Rewrite secure requests properly, to prevent SSL cert warnings (for example,
# to prevent https://www.domain.com when a cert only allows https://secure.domain.com).
# Note that the R=302 redirect should be set to R=301 in the final production site.

## RewriteCond %{SERVER_PORT} !^443
## RewriteRule (.*) https://mainsite.com/$1 [R=302,L]
## RewriteCond %{HTTP_HOST} !^(www)\.
## RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=302,L]


# If the server is not already configured as such, the following directive
# should be uncommented in order to set PHP's register_globals option to OFF.
# This closes a major security hole that is abused by most XSS (cross-site
# scripting) attacks. For more information, see http://php.net/register_globals.
#
# To verify that this option has been set to OFF, open the manager and choose
# Reports -> System Info, then click the phpinfo() link. Do a Find on the page
# for "register_globals"; the Local Value should be OFF. If the Master Value
# is shown to be OFF, this directive is not needed.
#
# Note: IF REGISTER_GLOBALS DIRECTIVE CAUSES A 500 INTERNAL SERVER ERROR,
# the server does not allow PHP directives to be set via .htaccess. In that
# case, this change must be made within the php.ini file. For commercial
# web hosts, contact the administrators/customer support for assistance.
# A host/server which does not support having a local copy of the php.ini file
# should include a php_flag entry for each PHP configuration variable having
# a non-default value; any PHP config variable not so specified will take on
# the value of its default setting. For more detailed information, refer to
# the documentation on the www.php.net site regarding setting PHP directives.

## php_flag register_globals Off

<?php
define('MODX_CORE_PATH', 'C:/wamp/modx_core/');
define('MODX_CONFIG_KEY', 'config');
?>