Today there has been a minor update to the Windows Phone 8 version Skype app. Version 2.6 improves reliability of chat and call notifications, improves reliability of calls to phone numbers and fixes for missing message previews in the recent conversation list.
You can find the updated app in the Windows Phone Store.
New and changed features:
increased chat reliability
increased call notification reliability
improvements in call reliability to phone numbers
Fix for occasional missing message preview in the recent conversations list
Via the Skype Blog.