Fraps can be effected by many things(CPU/GPU/HDD).
First off make sure you are recording to a fast drive if you can(A dedicated 7200 rpm drive is not a bad idea or at least a well de-fragmented drive[DO NOT DEFRAG if you have an SSD].).
A 7770 or 7750 are not ultra high end cards(much more of a mid end card designed to be the replacements for the 6770(5770) ), so they may have some effect.
I would try the use the 30fps cap on Fraps as well since it will reduce that data rate and may help things out. As a last resort lowering the screen resolution should help for sure.