Jason's suggestion first.
Also ask yourself if anything on this server may be doign more work during backups. You say WUS was just installed, but it doesn't seem like a likely culprit, unless you have it doing a repository sync during backups.
Try the single volume snap option, detailed here:
http://seer.support.veritas.com/docs/264464.htm
Are there any virus scanners running during backup? Disabling them may help.
If you paste some more information, such as the names of the various files skipped, we will haev a better idea what may be causing you grief.