What steps will reproduce the problem? 1.installing btstack (gps )

When i try and install btstack gps on the ipad ...it installs . then says reboot . Once i press reboot , the ipad sits with the apple logo forever . only way to get it working is to restore the software .

It worked fine before i updated to 4.2.1

right. the previous jailbreaks have been untethered. the 4.2.1 jailbreak requires that you connect your device to a computer and run e.g. redsn0w on every reboot. If you can, I suggest going back to 3.2, if not, just read up on "tethered jailbreak".

I was able to resolve this by running redsn0w and before the reboot process held power and home button to move iPad in an off position then followed then executed redsn0w and followed its instructions. In the future I will make sure to to a "tethered jailbreak" reboot.