hi,
good news about the hoster

(actually, you know, try it on your local dev server if you want, it's just a line to change in the php.ini file and a reboot

) and honestly no server would now be configured with the reg globals set to on, futhermore they are set to off by default in php5.3 which is the minimum requirement for revo
now, coming to the 500 error with the manager, that's funny, normally the manager is excluded from the root htaccess rules
in evo, it's in the root htaccess
RewriteRule ^(manager|assets)/*$ - [L]
in revo, if you use the root one, just use the manager one too which basically just says
if you haven't errors on your website you should'nt have in the manager either
have you checked the server matches all revo requirements (php5.3 with pdo, xml and so on) ?
have swing