Solved!
Use Root Explorer to rename Gmail.apk from system/apps to Gmail.apk.bak.
Reboot your phone and try again the install from the Market...
After install successfully you can delete the renamed version.
Sent from my HTC Desire using my fingers!
A new gmail...wow
Will make a update.zip if i am at home
With kind regards...Alex
Sent from my HTC Desire using XDA App