I have a friend that has been having these issues in a previous computer that he had and in a new one that he just bought; the first one had either Tiger or Leopard (not sure) and the new one has Snow Leopard (fresh install, not upgraded).

The problems that he has been having are:

• Sometimes he can't call people that are in his list.
• The performance of the program seems to slow down over time, and some of the contacts (both active or offline) of the list start to disappear
• Randomly the program freezes or becomes unresponsive, and he has to force quit

The basic things we have done to troubleshoot have been:

• At first he migrated his old computer to the new one (the old also had this issue), we formatted the computer and started Snow Leopard from zero, issue still persists
• We also deleted com.skype.skype.plist.

Not sure what else can be done? He also tried (just in case) the latest beta for Snow Leopard, but he's still having the problems.

Is there any other information I can give out that could probably help out? Console messages and such?

Skype also keeps a bunch of data and settings in:

(Home)/Library/Application Support/Skype

You may want to try quitting Skype, trashing that entire folder + the plist you mentioned, and the re-opening Skype.