If you don't have a relatively recent Nandroid backup of your phone (I used to do mine weekly, for just this reason), you may be best off doing something like this:
- from Titanium Backup Pro (get the pro version if you do not have it already - it's worth it.) Do menu->batch->backup all user apps
- If you need them, install SMS Backup & Restore and/or Call Logs Backup & Restore and back those up
- Restart in Recovery and Wipe data/factory reset, Wipe Dalvik Cache and re-flash xtrSENSE
- Set up from scratch again, though do not reinstall all apps. Reinstall Titanium Backup Pro and use menu->batch->restore all user apps. Do the same for SMS and Call Logs, if you need those.
- You'll probably also need to go through sound, display, WiFi, etc., settings to get everything set up as before, reset home screen icons, etc.
However, before that you could try uninstalling Lookout and see if that helps. Also, there is an app Cache Cleaner NG - try that, use it to wipe caches, and see if that helps. You can also use SMS Backup & Restore to delete all of your text messages (the app allows you to restore a limited number, if you need some for reference), and there is an app called Call Log Trimmer to delete call logs - that may help as well.
I'm not sure that either step will help, but I suppose it's better than doing the nuke and pave listed above.
I do have to say that, in my experience, the Sense build in 2.1 for the Eris, even rooted, eventually gets bogged down over time. Calls take several seconds to dial after engaging them, etc. Sometimes a simple phone restart helps, sometimes those things I listed two paragraphs above help, but sometimes you just need to restart from scratch.
Last thing that you can try (though I doubt it will help): Settings->applications->manage applications. Wait for it to refresh, looks for "Contacts Storage" (if there is no "Contacts Storage, try "Contacts"), tap it and tap the button "Wipe data". Do note that you will lose any phone contacts, plus any changes that you made since the last sync, but it may fix the sync issue. You may need to restart the phone if you are getting a force close, though.
Market links:
https://play.google.com/store/apps/...DEsIm9yZy5sc2FydG9yeS5jYWNoZWNsZWFuZXIubmciXQ..
https://play.google.com/store/apps/...mNvbS5yaXRlc2hzYWh1LlNNU0JhY2t1cFJlc3RvcmUiXQ..
https://play.google.com/store/apps/...nJpdGVzaHNhaHUuQ2FsbExvZ0JhY2t1cFJlc3RvcmUiXQ..
https://play.google.com/store/apps/...sImpwLmpvYW8uYW5kcm9pZC5DYWxsTG9nVHJpbW1lciJd
(One last note - if having access to sms and mms messages historically is important to you, I use an app called SMS Backup+, which creates GMail conversations in a label called "SMS" for all received and sent messages. They can also be restored, but they are easy enough to see in GMail as well.)
https://play.google.com/store/apps/...wsMSwxLDEwOSwiY29tLnplZ29nZ2xlcy5zbXNzeW5jIl0.
Also, do think about restarting in Recovery every week or so to get a Nandroid backup, just in case, if you don't already do this.