)Yeah, definitely make sure it's not some new software that's messing up your device. Mazingo did that to me - it stopped Notes, Excel, and NoteM from working.
As for Contacts, it very well could be b/c of the software compatibility. But also make sure that you don't use the a task switcher to close the Contacts program while you have a contact open. That will cause Contacts to not open up until you did a soft reset (and I realize you did do a soft reset, so this is probably not relevant, but it's a useful tip