“There was an error in XML Document…" and it gives a position e.g (39,-1099).
This can be caused by characters imported into the knowledgeable objects in the database which the .xml parser cannot handle. Look at the .xml file(s) in the \temp folder on the server to see at what stage the issue happened.
Also switch on diagnostic error logging (see knowledge article 97)and tracing to see if you can identify what character or object is causing the issue.
We may be able to provide scripts to strip these out – contact support for advice.
ITBM Core Knowledge