server problems 403, file not found

[Ampersand]

Hi, I would like to ask for a little help after server change. I have read already this thread, but problem seems to be somewhere else. Here is the situation:

• My hosting account was transferred within the same provider to another server
  
• I checked files and permissions - they are as they were when everything worked fine
  
• .htaccess files remained unchanged
  
• Two GS sites display fine, problems occur in /admin/ when editing files:
  
• In GS 3.0 - when trying to edit a file a GS page with 403.shtml appears (mysite.com/403.shtml)
  
• In GS 2.03:
  

1. I can edit&save components without problems
   
2. When trying to edit a page, after pressing save, a mysite.com/admin/changedata.php with The requested URL /files/ was not found on this server appears - Though the file is in its place, as usual, with 0644 in admin folder 0755.