That is what's causing you problems.
Antivirus is not needed on this platform and is a huge resource hog. It will slow down your phone tremendously.
Remove the antivirus and your phone will improve dramatically.
Really? Normally I would never question the "Hook" but I have Lookout on my OD and X2 and I do not see any performance difference at all on either platform. I've also read that malware and viruses are showing up for Android. Has this danger been exaggerated?
The danger hasn't been exagerated if you don't use your noggin. Read some reviews before downloading. Check out how many downloads there have been. If it's under 500, don't assume you just found some gem of an app that no one knows about yet.
Also, stick to the app store. A lot of the early malware was 4th party app download sights. (3rd party, being Amazon, etc...) Don't do it, unless you trust the source. Use your head and you should be fine.