You surely get an update of the Gmail application (>= 2.3.5) from the market or after flashing a new ROM.
With this latest Gmail application, Google introduced a limitation: the access to the Gmail message database is granted only to phone pre-installed applications.
I found 3 solutions to avoid this problem.
Remove the Gmail update:
– uninstall Gmail update in the Market (Market -> My Applications -> Gmail -> uninstall updates)
– in the Market, disable automatic update for Gmail
– uninstall Pure messenger
– reboot your phone
– reinstall Pure messenger from the market
– insert a fresh new widget.
Nota: Don’t skip steps … Pure messenger uninstall is VERY important. Pure messenger ask only once the permission to Android for the gmail access… If the access is denied, only a full reinstall will restart permission the process. It’s not my choice, but the Android architecture.
Use ‘K9 For Pure’ and configure Gmail with IMAP access.
The only way to bypass this protection of the new Gmail application is to use a modified version of Gmail and install it as ‘system app’.
This modified version will be the same as the current market version but with ‘old permissions’ allowing Pure messenger to read it’s message database.
Now, the drawback: to move it, you need to be root… you can follow this guide to install it.
I think the operation will need to be done on each new release of Gmail … so, don’t update Gmail from the Market.
There is an additionnal guide here to learn how to create your own version of Gmail.