new head unit only 1 speaker works now?

Hello all. I just installed an aftermarket car stereo for the first time. I'm doing this in my 2000 Jeep Grand Cherokee. I was given an Alpine CDE-121 stereo for Christmas. So I went ahead and purchased the mount and wire harness adapter from Crutchfield for install. I called Crustchfield tech to make sure I was connecting the ground correctly, etc. After connecting the stereo harness to the adapter harness and powering on the unit, I only got sound out of my front right speaker and a little sound out of my left tweeter. I double and triple checked all my connections. So, I disconnected the adapter harness and reconnected the old factory stereo directly through the vehicle braided wire harness, fully expecting that to play through all speakers...in which case, I would check my connections between the head unit harness and adapter harness again. However, to my surprise, now the factory stereo would only play through the front right speaker. Everything was working fine before the install. What could I have done? Any help and direction would be greatly appreciated! Thanks. P.S.- I had to replace a power window regulator several weeks ago in the front passenger door, and it happens to be the only main speaker that is working now (aside from the driver side tweeter). You would think if I didn't reconnect that speaker wire correctly, it would be the one not working. I tested the stereo after fixing the window regulator though, and the stereo system had no issues. I've done readings with a multimeter, touching the probes to the terminals of the positive and negative wires of each speaker at the factory harness for the head unit. The readings confirmed what I am hearing...or not hearing. The front right speaker showed continuity and resistance of around 4 ohm. The other 3 speakers did not show continuity, and had resistance readings all over the place. 2 were above 10 ohm, and 1 was below 1 ohm.

the meter doesnt lie. you either have blown speakers or shorts in the speaker wire. it is possible that the radio was defective from the start and when you plugged it up it might have sent dc current to the speakers causing them to blow.