Default Why would this icon appear?

I switched on my HTC TP2 this morning and opened an application called apMemo, to write a handwritten reminder. But a spurious icon appeared, preventing my using it properly. It was the same icon I see when I go the Phone screen, midway between Contacts and Menu. The one for toggling the onscreen keyboard.

I exited and reset (oh how I wish that didn't require taking off the cover, a feat I rarely manage successfully!) and that appeared to solve the problem.

I'm an end user, not a developer, but would appreciate someone explaining what might have happened here please. Does it sound like a bug with apMemo which I need to report to the author?

P.S. On trying to post this I'm getting a message saying I'm not logged in, yet I am! (At the top of this window I see 'Logged in as terrypin' I'll try again ...

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Terry, East Grinstead, UK