For about 2 months – ever since upgrading to Leopard – I have been unable to answer incoming Skype calls on my iMac because the “pick up call” dialogue box is never shown; the software just rings and rings and there is no way to get the software to pick up without clicking the (nonexistent) answer button.

I tried switching off “Spaces”, I reinstalled Skype, blew away the configuration directory… finally, after an evening of experiment, I tracked down a solution:

I have successfully fixed this problem by quiting skype then deleting the two skype preference files (com.skype.skype.plist). Make sure you get BOTH of them – confusingly they have the same name. One is in /Library/Preferences, the other in ~/Library/Preferences. Spotlight for ‘skype’ finds them both. Then when I re-started skype it ran through the setting up drill as if it was a fresh install, and the answer/reject dialog appeared on the next call.

Happy now.