Not seeing this issue *yet*. Then again I don't have any stock, non-rooted devices
AFAIK you don't 'search' for updates. You open the market, go to your 'My Apps' and see if they show up as needing an update. You can also select a individual app and it will show if there is an update available also.

Some apps don't update for months at a time others seem to update weekly. I generally check an app for an update when some buzz about it hits the web.

*EDIT*
Phone one with out issues is a Original Droid on Verizon with Cyanogen Mod 7x
Phone two with out issues is a HTC DESIRE HD on AT&T with Cyanogen Mod 7x

Carriers can and do dink with the market so it is possible that T-Mo is doing something?
Do you recall which app/s didn't update?
Also possible that memory corruption is in play...