I have updated 2 iMacs and 1 Macbook to 10.5.5 recently and all three of them have started giving this Time Machine error occasionally (every few days). The Macbook and 1 iMac are backing up to an AEBS disk, but the other iMac has a direct attached USB disk (both are WD MyBooks). I have never had a Time Machine error on any of these machines before. The most recent error from the iMac with the attached drives is:
1/13/09 11:20:37 AM /System/Library/CoreServices/backupd792 Error: (-43) SrcErr:NO Copying /Users/dwhitti/Library/Preferences/Macromedia/Flash Player/#SharedObjects/2MDSQCJD/a.ooyala.com to /Volumes/Danny's TimeMachine/Backups.backupdb/dwhittingtonmac/2009-01-13-112032.inProgress/ACD16566-3746-4929-B9C9-0AE4DB0CCBE7/Macintosh HD/Users/dwhitti/Library/Preferences/Macromedia/Flash Player/#SharedObjects/2MDSQCJD
1/13/09 11:20:37 AM /System/Library/CoreServices/backupd792 Error: (-43) SrcErr:NO Copying /Users/dwhitti/Library/Preferences/Macromedia/Flash Player/#SharedObjects/2MDSQCJD/a.ooyala.com to /Volumes/Danny's TimeMachine/Backups.backupdb/dwhittingtonmac/2009-01-13-112032.inProgress/ACD16566-3746-4929-B9C9-0AE4DB0CCBE7/Macintosh HD/Users/dwhitti/Library/Preferences/Macromedia/Flash Player/#SharedObjects/2MDSQCJD