Romeo,
before you report a bug though, could you please update to a newer build (best is the current build, and this is what we ask you to use for confirming bugs because it could be that it's already fixed).
From the revision you state, I assume you are using daily builds and there was a bug report for a problem that was introduced in revision 22222 (last daily build before r22215, August 9th) and fixed in revision 22264 (next daily build August 13th, r22286) and your description reminds me of it. You should update anyway as explained above.
(For anyone wondering - I'm thinking of
http://www.rockbox.org/tracker/task/10505 which could hit here to as it was confirmed on greyscale targets and the Iaudio remote (M3 main screen) is greyscale.)