Posted earlier today on XDA by pulsar_g2:
Full post is available here.Recently there have been a number of issues with the Android market, which are caused by Google. This problem is at Google's end, and doesn't lie with the developer of your ROM.
It affects people using the Nexus 1 with stock ROMs, and it also affects custom Hero ROMs. There's nothing your ROM developer can do to fix this, so there's no need to keep reporting it.
As of now, the following "workarounds" may exist, although none are sure-fire fixes.
- Clearing Google Market app data in Menu > Settings > Applications > Manage Applications
- Get the file /sd/download/DownloadFile.apk and manually install it
- Run the command "adb shell rm -f /sdcard/.android_secure"
None of these are likely to fix the issue, but these are the known "workaround" ideas some people have suggested. Really the only fix is to wait on Google to sort out the market.