There's an older discussion thread in this forum regarding this issue, problems with the temp files used by the client can cause this behavior.
Here's my post regarding this issue posted earlier, I'd suggest reading the previous posts there as well:
http://www-10.lotus.com/ldd/nd6forum.nsf/ShowMyTopicsAllFlatweb/477d2fa01354e2c185256e150057aabc?OpenDocument