Ok, here's my solution and it seems to be working for the past few hours on my rooted droid x with all the latest stock stuff:
1. I have set the battery prefs to full optimal.
2. I have uninstalled all of my task killers and restarted.
3. If you want to use wifi set it it to "never sleep" (This is in the sub menu in wifi settings! Go to Wifi settings, then hit the settings button again.)
4. Set data manager to "Data Enabled"
Since I did all of these things, I'm not sure which one was the cure.I think they are all important but I'm pretty sure it was the task killer that was causing the main problem. I'm actually not burning a lot more battery than I was before but if you want to keep killing tasks, i suppose you can delve into trying to figure out WHICH task needs to be kept alive if you want or you can make sure it isn't killing tasks when you lock the screen as some task killers do.
I'm surprised the geeks over at Sipdroid haven't been on this. Maybe there will be a fix in the next update.
--jon