whats this message in log file??

[isteana]

sometimes i got this message on ioBanana_err.txt

ioBanana_err.txt:

06-04-07 01:17:18 zscheckZip 4: error processing zip file (13).
06-04-07 01:17:20 zscheckZip 4: error processing zip file (13).
06-04-07 01:17:21 zscheckZip 4: error processing zip file (13).
06-04-07 01:17:24 zscheckZip 4: error processing zip file (13).


whats this message?? i dunno whats mean
then how can i fix......

help me plz..