Steam backup troubles

[Paulaner]

Not strictly related to Half-Life.
I am having troubles making a backup of a Steam game (X2 - The Threat): the backup process stops ten seconds before finishing, and Steam freezes. I tried on different machines, with different Steam installations. Anyone can help?

 

[Paulaner]

The same problem with X3. All my other Steam games are OK. Is there something in the structure of X games that crashes the compression process during backup? What a strange thing.