Trackpad not working on home screen only (Curve)

I use an old Curve (9320/7.1.0.907 (B2494) for odd tasks, but in the last few days the trackpad has stopped scrolling on the home screen.

They keyboard still works.
I can scroll if I open a menu in the home screen.
Scrolling still works in some apps (not the MemoPad)
Clicking with the trackpad works fine.

There haven't been any software changes in months, and all network connections are disabled.

I've done battery pulls, soft resets/restarts and alt+shift+delete resets. I'm loath to do a factory reset in case I can't recover from it.

Any ideas on how I can try to troubleshoot/repair this?

Thanks in advance, folks.

- RG>