Many of thes kind of scope have an Dallas chip with an integrated battery cell, when the cell eventually dies you may get some problems
Try to find any user manuals and or service manuals, even if they dont have schematics they provide help
Could be hard drive corruption, a sudden shut down may have created some problems
If the SPC has gone well, it could be a simple problem, they are windows based, and like any OS, normally you have to do a proper shutdown
You have some tds5k series thread here, if you can, grab at Tektronix every files you can find, like software re installation / drivers etc ...
We have an tds 7k seria at my job, i use control+alt+delete to bring the task manager, i kill tektronix software, i run a new task : explorer and that way i did vxwork and others repertories / files backup on a usb key etc .... and run scandisk ... the hardrive is old, and im sure it will die, i have all backed up in case of ...
And it was the dallas chip in it who played bonkers in my case its an ds1245 dip, not the special dallas pcb / clock "old model"
And pls be careful, they are sensitive stuff in them, take proper anti static measures
A good dust clean up would be help ful too