Zip as in Winzip?
55Mb in 30 minutes is so long there has to be a fault somewhere. 30 seconds ought to be enough.
Have you tackled folders of that size before?
Or are you running something else in the background now?
I'm only guessing, but you might be a little short on RAM. Perhaps low on free space on the HD?
When you post back, say what O. system you use and how much RAM you have. Also do say if you have added any program or changed some hardware recently.