Turn on error reporting and logging and check server error logs, let us know if you have found something interesting there (fatal errors, warnings, notices, anything...).
The only things I discovered are irrelevant to others. Didn't have access to the error logs on that server, nor could I enable error reporting. No matter, I did find the cause: there was simply a problem with the authentication check (rather weird issue with interpretation of relative paths) -- ie. something wrong with my code, not CKFinder's.
Re: XML Parsing Error: no element found
Wiktor Walc
CTO, CKSource - http://cksource.com
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Re: XML Parsing Error: no element found
Thanks for you reply, anyway.