Strange Manager Windows

Client Side of Web-Site works fine and all content are correctly displayed.
However -> After entering /manager
1. i get two Notice:
Array to string conversion in /home/xxxxxxx/www/xxxxx.xxxxxxxx.ch/core/xpdo/xpdo.class.php on line 478
2. Manager Window with all Menu-Items are displayed but there is no content displayed. Only on certain Windows the left inche is filled with meaninfull content but i'm unable to enlarge this window-part.
I can access via ftp - what can i do?

try deleting the cache via FTP:

log out and delete all files in core/cache/

then try to login again.

Thanks alot.
Did all you've proposed!
No success.
Is the PHP Version having an impact. (ModX 2.1.5-pl)
Regards
Solenthaler [ed. note: solenthaler last edited this post 9 years, 11 months ago.]

The Problem has been fixed by backing up to PHP Version 5.3.
Will update to newest ModX version and try over with PHP 5.4 and 5.5
Thanks again Achterbahn
Cheers Solenthaler