360 Controllers not turning on? (all 4!)

Ok hopefully someone can offer some insight to this problem.

A couple weeks back I purchased 2 black wireless controllers so that 4 of us could play halo 2 at the same time. Things were working ok , until a couple days later I couldn't get one of them to turn on to save my life. I wasn't in the mood to bother troubleshooting so i went to bed

A couple days later, I tried turning on each one in sequence. None would connect. Before anyone asks, the 2 black ones were using the almost brand new batteries they came with. The 2 white ones are using fully charged battery packs. Also, i have tried sync'ing them up multiple times.

This happened again last night. All 4 of them just flash and flash and flash. My gut tells me that they just aren't making a connection with the 360 for whatever reason - but here is the strange part. If I turn off the 360, all the controllers stop flashing. That means something is working.

Thanks for reading, I hope someone has an idea. (Halo 3 is coming and I can't have this thing sent off to microsoft for 2 months. May just have to buy another xbox. damn ms!)