Software Update Service

I have SUS Server running on Windows 2000 Server. I ran well for few days before I fail to do synchronization. I received this error message:

Errors:
Failed to download from URL ‘http://www.msus.windowsupdate.com/msus/v1/aucatalog1.cab’. (Error 0x80070008: Not enough storage is available to process this command.)

I still have 1.5 GB on the drive where I set the update to be stored.