I would like to thank everyone who posted comments on the previous post about Skype crashes. In particular I'd like to thank James who suggested updating Cydia mobile substrate. It looks that this update does fix the problem and I have not experienced Skype problems anymore.
So, if you do have a jailbroken iPhone make sure to apply the Cydia mobile substrate update. Just run the Cydia application and it will show this update in the changes section.