How can I download apps again after changing my Google account password? I changed the password for my Google account earlier, and since then, every attempt to install an app results in a download was unsuccessful error. I have not been prompted for my new password anywhere, so this is highly likely to be the problem. How do I fix this?
You cannot remove the "main" account that is linked to your market account, at least I have never been able to when I tried. 

I would try rebooting the device, then turn off all "syncing" for that account. I would even reboot again after turning it off. Then turn syncing back on.

[edit]
I've also read that someone did the following:


Changed Password via web browser
Opened gmail application
hit Menu -> Refresh
The refresh will fail, but there will be a notification to enter new password.