as2000 takes a day off

[kribo]

i have an as2000 advance ed.(built 1086). on a win2k w/ lotus domino on it. for the last couple of weeks, what i've notice is that the backup takes a day off every tuesday. here's my backup schedule, [m,t,w,th and su] i skipped friday night in favor of sunday instead. what i don't understand is, why does the backup skip tuesday night and while all other days are backed up fine?
i'm not sure of any changes that might have triggered this inconsistency. if anyone has encountered this problem or have an answer please let me know.


thanks,
yan