X Error of failed request

[bill lam]

Sometimes (about 3 or 4 times in one day) that it just crashed with this message,

X Error of failed request:  BadWindow (invalid Window parameter)
   Major opcode of failed request:  18 (X_ChangeProperty)
   Resource id in failed request:  0x4400003
   Serial number of failed request:  1113
   Current serial number in output stream:  1117

no stack trace was available. Is this a known issue and how to
get more information that may help debugging.

I use nvidia card on ubuntu 7.10 amd64.

regards,