Thanks Josh,
I appreciate the insight. I have researched other possibilities such as low quality links, high number of inbound links across the same domain, etc... but those competing for the same search phrases seem to be equal or worse offenders and are unaffected.
The primary difference apparent thus far is the less than SEO optimal domain usage.
But I'll keep digging and live with the .co for now as it sounds like the first domain change was one too many.
Cheers,
-Ross