After trying many combination I have finally an ATT curve working with my T-mobile with all themes unlocked and no Push to Talk.
PTT is useless for me as for many. Therefore you can free some memory and have your curve run faster.
Files below were tested with O2, Att/Cingular and Rogers latest OS.
Download, unzip and place both files in :
C:\Program Files\Common Files\Research In Motion\Shared\Loader Files
File blackberry.alx will unlock all themes
File platform.alx will remove PTT
Once you have installed both files you need to remove vendor.xml from your pc:
C:\Program Files\Common Files\Research In Motion\AppLoader\vendor.xml
Then connect your curve to the PC and launch Desktop Manager.
If no message is shown during synchronization then launch Application Loader and simply press next a couple of times.
Your device will reboot automatically. Unplug after reboot and enjoy your new themes.
Download files here.