Car Stereos: 2000 Accord aftermarket issues, factory antenna, antenna connection

Question
Scott,
 I put an aftermarket radio in my Accord. Install went well, no problems. Did all my radio presets. Everything worked perfectly. Next day, half the presets are not working. I push the button and the station pops up on the screen but...static. Now, my factory alarm activates for no reason. It never did this in the past. Scared the @#** out of me. Now I'm thinking that the "Anti Theft" factory radio (now removed) and the Security System are are not "communicating."

So, before I put the OEM radio back in, grrrrrrr. I'd like to hear some opinions on how to resolve this issue.

UPDATE: I put the factory back in and all works well.  So, I took it out and put the aftermarket back in.  No more "Alarm" issues but...I have no AM and my FM stations are limited to very local stations.  Checked and rechecked the antenna connection.  It is securely installed.  The radio workrd great in my 89 Prelude.  

Any suggestions?
Thanks, Chip

Answer
Chip, good job on getting by the alarm issue.  However, I do not think the antenna is doing its job.  Is the antenna connection very tight?  Or does the thing just lock in, but still wiggle.  There are a couple different size factory antenna wire connectors.  Yours may be a smaller one going into a larger hole, but if it is not really snug feeling, it is not working.  If that is not the problem, I would suggest trying another radio.  Hope this helps, Scott