What vintage Mac are you using? What version of the OS?
In general, I'd recommend you try doing the following:
* Uninstall Skype completely. Your best bet for doing this is to download App Cleaner, a free, complete uninstall application for the Macside. I use it on all of my Mac users' Macs at werk and have come to depend on it to find and trash all of the 'hidden' preference and library files.
* Install and run YASU (Yet Another System Utility). YASU is a pay-what-you-want software package. I use it on my werk Macs as well, and it does a great job of cleaning up things in the background (think Rebuilding Your Desktop in the old System 7-9 days) as well as doing a permissions check.
* Boot your Mac off of your install DVD and do a permissions repair from there as well.
I've had odd problems with various versions of Skype on my werk iMac (running 10.7) where the app will crash if I try to open my Contacts list. No idea why it happened, nor why it stopped happening. I'd suspect their Macside app is a bit buggy, but I have lots of Macside friends who use it on a daily basis as part of their werkday.
Let me know if any of that helped.
p.s. Apparently I haven't posted enough here yet to include the URLs for those two apps. You'll find them easily enough if you consult The Google.