What model of PVR do you have? How old is it -- especially the disk-drive inside the PVR ?
Disk-drives do have a limited life-span -- being unable to delete a recording from it is a sign that the disk-drive could be failing.
Your PVR probably is "out of warranty". So, it hurts nothing if you remove its top-cover, and then inspect the paper label on the disk-drive, to see the "manufacture date", which usually is in "YYDDD" format, e.g., "10180" would the end of June in 2010.
Looks like a Shaw update. Box was showing not subscribed to Global TV today. Rebooted box again. No message on Global and was able to delete programs that I was not able to before. That’s good. Shows software issue rather than hardware issue.