I've problems purchasing / downloading NavDroyd from the Android Market

Since the beginning many users complain about problems downloading / purchsing non-free applications from Google's Android market. The only help we can give here (since Google is not able to solve these permanent problems) some tips gathered from the Internet Here's a quick and dirty collection of all the possible fixes:

• Market downloads hanging
• Paid apps that won't complete the purchase process (such hanging at "Authorizing Credit Card")

Clearing cache and/or data for the following apps (Settings > Applications > Manage applications)

• Download Manager
• Android Market

Power off, remove battery and/or SIM card and/or SD card, wait, re-insert, power on your device again.

As of this post we never found a permanent fix. Google has been silent on the issue.