Same thing happened to me! I've had nothing but problems with my phone since the "upgrade" to Froyo. (Every time I talk about Froyo now, I put quotes around "upgrade", because it certainly hasn't improved my Epic!!
)
So, after the "upgrade", the biggest problem has been the random reboots and freezing, and especially after using Bluetooth and disconnecting from my car. Also, LauncherPro would constantly freeze, so I thought maybe it was LP that was causing the problem, so I uninstalled it and went to TouchWiz. I was using TW for about a day, and I was actually liking it a little bit, and I wasn't having any Bluetooth issues anymore.
But then yesterday I had my Bluetooth engaged and I went to activate the Navigation app and it froze up again, and wouldn't respond. I pulled the battery again, and since then I keep getting the TW force closing issue. It won't start at all now.
With some quick finger actions, I was able to get into settings before the force close and clear the home launcher default. I was then able to get into the market and redownload LP. I've tried clearing all the cache and rebooting over and over, but TW just won't work. LP and the Sprint Launcher works, but not TW.
I haven't done a hard reboot yet because I've had to do it twice already after the "upgrade", so I'm just gonna see if I still have problems with Bluetooth and LP....What a joke these damn phones are :-\