I cannot get computers to see my 770 when it is connected by USB. I get the USB icon on the 770 screen and it says that "PC connection alive." I have tried this on Windows XP and on Mac OS X and neither detect the device at all. No error messages, no "new hardware found" messages or anything. On the computer end, it is as if the device was never even connected.

I tried putting the 770 into peripheral mode but that didn't work.

I am guessing something isn't set right on the 770...I am hoping it is not a hardware defect. Any suggestions?

Try plugging it in with the cover on and with the cover off and see if it makes a difference.
Maybe also try reseating the memory card.

Thanks, I tried that but USB is still not recognized :-(. Is there some setting that I may have wrong? Could it possibly have to do with R&D mode? This is a research unit, so another student had it before I did. I am not sure if something may have been toggled before I received it.

Try hooking it to another PC. If it fails there, then it is not the PC, but the 770's setup. If it does works there, though, then your PC doesn't recognize it right.

If so, then look at the PC, in Settings->Control Panel->Administrative Tools->Computer Management->Device Manager. You will probably find it there with an X next to the icon or something like that.

You are sure to put it into peripheral?
You restarted ke.recv?
I do:

echo peripheral > /sys/devices/platform/tahvo-usb/otg_mode
/etc/init.d/ke-recv restart

It should work.

I have this same problem. When I first received my 770 the USB connection worked, and then one day it just stopped working (2005 OS). I tried many things to fix this and none have worked, including reflashing and updating at every OS update. It's not a big deal though, as you can access it via wifi (ssh, scp), gmail-hack, mounting, or a card reader. I actually prefer these methods over the USB connection.

My 770 has been in R&D mode for about 11 months now. As with Joshua, mine stopped being recognized on whatever PC I plugged it into. In the meantime, I just mounted my PC and copied stuff directly over the network. Now, where it gets weird, USB xfer magically started working again one day.

If you've got access to linux, use the flasher and try to flash it into slave (ie disable USB hostmode if it's enabled). The method above should accomplish the same but going the flasher route is always a nice backup strategy.

As I've mentioned before, I'd disable as many background processes as possible/practical before flashing. I think some tasks interfere with flashing. Note that I don't experience problems flashing from linux, just Win XP.

My 770 is in R&D mode since I bought it. (1 year), and its in Host mode, since I flashed the first time.
Before OS2006. if I switch it off, when I restart it, was in the same mode as was on, but with the OS2006, every time I reboot, it comes into Host mode.
I made a little script to put it into host/peripheral and it runs in the cpu/mem aplet.
The only thing I have to improve is that if the 770 is in host mode and I connect something, it have some problems with the swap that I have in the MMC. So I have to modify the script to swap off before change the mode.
The best thing that you can do (I think) is to reflash with --enable-host-mode in linux.

you need to run disk manager in windows and then reformat the mmc card so that windows can recognize it