Problem in Quartus: After saving a text file, Quartus want's to reload file

I have a strange problem with Quartus 13.0SP1 on my computer:

When i do some changes in a text file (TDF), save the file to disk and change to another window, quartus shows always a dialog box with the following text:

"Do You Want To Reload The File?"
"File ... was changed. Do you want to reload the file, possibly overwriting portions of the file, including any saved changes?"

This happens, when i switch to another open text file and back to the modified file. It also happens when i open and close a search dialog or any other dialog.


The other strange thing is, when i answer the dialog with "Yes", the file gets reloaded from disk and all special characters (for example "ä", "ö", ...) are no longer interpreted in UTF-8.
When i close the file and re-open it, the special charactes are displayed correctly again.

This problem also happend with earlier quartus versions (12.0, 12.1, ...).
It seems, this problem is specific to my computer (Win 7, 64bit), my colleague uses the same quartus version with the same operating system and he does not have this problem.

Maybe it could help to reset all quartus settings to default values, but i did not find out where the quartus settings are saved.

Has any one else have the same problem?