Roger - You may want to experiment with COMPRESSAlways=No on some of your more "interesting" clients. It can impact client backup performance where a whole transaction has to be re-done, but will save you from the server issues you're encountering.
To deal with the individual problem files in the stgpool, you might try using Virtualnodename (if available for the platform type) to restore the problem file to a like system and then back it up again without compression or COMPRESSAlways=No. A Deleted Backup or EXPire command at the proxy client may be suitable to clear the thing from the stgpool. Richard Sims
