Could be your dongle.
Stick a Blue Cube or Belkin on it. It has solved over a dozen of these same sort of power problems here at Geekhack.
It could be any combination of insufficient current from the USB port and dried-out electrolytic capacitors in the board... and the adapter is not entirely out either. Maybe try another known-reliable adapter or computer.
Then again, it only flaking out after a few seconds is strange. Sounds like it could be a thermal issue or something related, like a bad solder joint.
The escalation plan would look something like this:
1. Try another adapter and/or computer to make sure it is the board.
2. If so, open up board, inspect solder joints with magnifying tool, esp. those for power (+5V) connections at cable lead-in and microprocessor. A flashlight on the backside of the PCB might help find hairline cracks (hopefully none).
3. If that doesn't turn up anything, write down the values and form factor of electrolytic capacitors (usually there aren't more than a few on there) and replace those with new ones for good measure (same capacity, same or higher voltage rating, mechanically fitting).
I'm back now with a blue cube. This time, the keyboard actually works but not properly (I have to type one key at a time somewhat slowly). When I start to type faster: liketnw, hn i stat having probleeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee (it's supposed to say "like right now, then I start to have problems").I would try it on a native PS/2 port and see if it works properly. FYI, I use an adapter that shares the chipset used in the Belkins, you can check it out in the adapter wiki. My friend played typeracer plenty of times on that board with an adapter and experienced no problems whatsoever.
Basically when I type fast, some keys aren't typed out (I noticed some input lag too) and if I continue to type fast, then thisssssssssssssssssssssssssssssssssssssssss happens and I have to retype the dragged out letter to stop it from continuing (in this case, the letter "s").
How would I diagnose something like this? Follow keyb_gr's advice or is this keyboard FUBAR?
I would try it on a native PS/2 port and see if it works properly. FYI, I use an adapter that shares the chipset used in the Belkins, you can check it out in the adapter wiki. My friend played typeracer plenty of times on that board with an adapter and experienced no problems whatsoever.
The Blue Cube DOES have the same chipset.
And it's the one PCkeyboards recommends. They would know.Show Image(http://www.clickykeyboard.com/1391401.jpg)Show Image(http://www.clickykeyboard.com/model-m.jpg)