since ashort time ago (30 minutes or so) I can't download any file to my 2 NXT anymore.
"Failed to open Communicatio link to NXT brick.
...
Error Code:
Fantom Err: 'Firmware Download Failed'

Why this?
Nothing severe had occured, everything's like before,
Brick is switched on,
Windows recognizes that NXT is connected via USB (device manager: LEGO MINDSTORMS NXT, USB\VID_0694&PID_0002\0016530119E8)

But RobotC can't find Brick via USB ? ! ?

RobotC deinstalled, rebooted, new installed (v. 1.10): Error remains the same!
Same error with both of my bricks!

EDIT:
Tried do download the original Lego firmware to the NXT:
Not possible,
No bricks detected as well.
Tried to reset 1 of my NXTs:
Display stays empty, NXT "ticks" like a clock,
connecting it via USB: Windows recognizes USB device ("dong-ding"),
but neither Lego nor RobotC get a connection.

What might be the reason?

problem solved:
USB device driver was installed, but had a failure.
new installation of NXT USB Device driver =>
everything's ok!

I am also beginning to have USB port problems as well. Last night my Mouse and keyboard stopped working. Both are using USB ports.

I had to finally switch my mouse to a USB port on the front of my CPU to get it to work and it works fine and the port on the back of the CPU is dead.

I just had the same thing happen a few minutes ago, and I again had to switch my keyboard to a port on the front of my CPU.

The first time it happened, I was starting up a NXT that was connected via USB. Tonite, it happened out of the blue for no explained reason, but the common thing I have noticed is that RobotC was open and running.

Something is happening and I have no idea what it is. Can RobotC mess up the USB ports??