I just repaired a system last week with the exact same symptoms plus a few others. The other system had problems with the short recordings on the drive as well. He lost the ability to fast forward as well. Upon hitting the 30 second skip button, the show would just go to the end of the recording and show the blue done screen. His problem ended up being drive related. His hard drive is failing and after a format of the recording harddrive everything works now but I am sure the problem will resurface untill he gets a new drive. If you have another drive I would try switching the recording to a different drive and see if you can get through a recording. If that works, then try to format the recording drive and see if thats gets you back working.
Good luck and let us know.