HP Printer 5100tn – Unexpect Paper Size

I am having problems printing to a 9.9cm x 10.9cm flyer on a HP 5100tn printer. When ever I try to print to this particular sze paper it returns the message 41.3 Unexpected Paper Size – Expected A4.
I have researched this and see that it is a problem with the paper size that that tray is expected to deliver, except I am printing to the manual feed tray, and I cant see any settings to alter an expected size for this.
Can any one with experience in this printer and problem please help… Ive tried everything I can think of. Thanks very much.