Try taking out the battery (turn the phone off first), leave the battery out for a minute or so, then put the battery back in and restart the phone. That's a full reset (you won't loose your data) as opposed to just a reboot - maybe that will help.

Also, have you downloaded any new apps? If so it might be time to consider uninstalling them.

 

Take it into the store. I had this same issue with my first Eris and the said it wont connect to the verizon network for whatever reason and they had to replace it.

 

My Eris did this last night.
I must have rebooted it 10 times trying different fixes and uninstalling everything I had installed that day.
What finally seemed to work (I assume this is what worked since my phone started working after I did it) was to turn on airplane mode (one of the few functions that was still working), do a graceful shutdown (power button), remove the battery, wait one minute, replace battery, turn on phone, turn off airplane mode, and it started working again.

I cannot completely confirm this is what fixed it. It could have just randomly started working, but it makes me feel better think otherwise.

 

My Eris seems to only do hinky stuff when I'm using Slacker. Reboots, deletes contents of my card, makes randon calls when not being touched at all. It also seems to rebooted from slacker and reboots when I get an email notification.

It's strange but beyond that, no other probs since the update. Battery life post update is awesome though.

 

This happened to me too. After the update, when it rebooted it started doing this. I did a factory reset and all was fine. Then the next night it did it again, and I did a factory reset again. Now, a week (and 1 day) later, it hasn't happened since.