I was getting an error when doing CVS actions in Eclipse at work:
Error: MyProject: cvs server: CRC error uncompressing AllProjectSummary.java
Error: MyProject: aborting due to compression error, file AllProjectSummary.java
My guess is that it happens when talking to an older version of the CVS server. I worked around the problem by disabling compression. In Eclipse, go to Window->Preferences->Team->CVS->Connection->Compression->0 (disabled)