"Package was not signed correctly"

[infantry667]

Custom ROMs do NOT come with their own apps, they just customize the way that app appears along with everything else they customize and they sometimes remove the stock, or "bloatware" apps that come with the phone. The only reason I can think of is that there is a problem with the way the market sees your phone, now THIS may be because of the a custom ROM. Your best bet is to use a ROM that changes the version of the app market that is installed on your phone so you don't have compatibility problems such as the one you are having. The only other reason I can think of is that you might be getting apps through another market app (perhaps one that offers paid apps for free?), in that case then this is happening because the app source is different than the original android app market and is way beyond "third party" app problems.

SBF'd (sent blazingly fast) from my Hulkified X2