Users have reportedly been having problems seeing apps in the market for some time now. Specifically, users of the HTC Desire and HTC Legend overseas have been unable to see certain apps (such as Twidroid, amongst others), however the Legend’s problem seems to differ from what Desire users suffer from. The problem – which seems very trivial and foolish – is that those apps were unable to see the camera on the phone.
HTC has acknowledged this and will be beaming over a quick update to your phones very soon. Your phone should scream at you (or beep, I forget which) when the update is available. This still seems to be unrelated to copy protection, though, which Google has yet to address.