Onscreen Fitaly on Palm Vx Crashing

I am running Fitaly Onscreen 1.0 on my Palm Vx. (Palm OS ver. 3.5.3)
When I'm in say Datebook5, and then switch to the note field of an appt, as soon as I start to enter text via the Onscreen Fitaly, my Palm crashes. I get a Fatal Alert that says:
MemoryMgr.c,Line:4450,Invalid chunk ptr (Reset)

The crash doesn't seem to happen w/any certain sequence of strokes, etc, but rather when I try to switch in-between parts of an appt. (I know that's vague, but best I can describe it.)

What does the MemoryMgr.c, error mean and what do I do to fix it?

I had a previous version of Fitaly Stamp, and LOVED it. However, the Palm that was on was lent to my dad for a temp replmt of his crashed IIIc and I never got it back. So I bought a Palm Vx used on Ebay. I replaced the digitizer/screen and it's been working fine since... that is until I tried to start using Fitaly again.

As a side note, is there a way to get Fitaly Stamp "reinstated" and then upgrade to the latest version? I loved the stamp version and I'm not terribly fond of the onscreen version. I honestly don't remember how long ago I purchased it, but I know I don't have any stamps here now.
But I digress.

Thanks,
Drew