restriction digestion against colony PCR - (May/09/2011 )

hey every body
I wonder if any of you has experienced the situation in which I am trapped.the thing is my recombinant colonies which have shown a positive pattern( using specific primers) wouldn't give the correct fragment sizes in agarose gel electrophoresis performed right after the colony PCR.
I would be grateful for any piece of advice or hints you could suggest.

all the best
Mahsa

Please be aware that colony PCR is not a reliable method of verifying colonies and is subject to errors such as contamination. Restriction digestion has the final say.