This issue exists only in the 9.1.2 release. It has been fixed with the release of 9.1.2 SP1.

Problem: The directory in which the temporary report files are stored has reached a limit of 65,536 files.

Fix: Browse to C:\Documents and Settings\<user>\Local Settings\Temp for the user who is experiencing the problem and delete the temporary files from this directory. Note: Delete only the files, not the subdirectories.