Arduino no longer recognized

I was working with an Arduino UNO and a spark fun Serial GLCD connected to the TX-> pin through a 1k resistor.

I had a intermittent power issue with the LCD so I fiddled with the wires although I don't think that anything shorted.
I then made some changes to the code and hit upload only to be greeted by "COM7 not found"

So I unplugged the Arduino and plugged it back in. Windows gave me a popup "USB device not recognized"
I tried another USB port an this time got nothing. Not even a change in device manager.

Removing the LCD display did not change anything either. When plugged into my Linux laptop there was no response from dmesg.
Strangely enough when I plugged it back into my Vista desktop and connected the LCD screens power connector it gave me another USB device not recognized popup so I tried the same thing on Linux and after several times dmseg spit out

USB 5-1: new full speed USB device using uhci_hcd and address 21
USB 5-1: device not accepting address 21, error -71
hub  5-0:1.0: unable to enumerate USB device on port 1

Writing to /dev/ttyACM0 (which was assigned when it was working) succeeded and even made garbage display on the LCD but attempts to change baud rate caused "Inappropriate ioctl for device"

I don't see why it failed. Did I seriously fry a third serial to USB convert chip?

Try a different USB cable.

Just tried another one (albeit loose fitting one) and no result :frowning:
New information:
I jumpered the pins to reset the 16U2 and windows gives me the device connect sound and pops up "Windows needs to install driver software for your Unknown Device"

Edit: Oops mine has a 16U2 not 8U2

I fixed it!
After resetting the 16U2 it showed up as an unknown device. I then installed the Arduino UNO drivers but it didn't work.
It gave me a Code 10 in device manager.

So I downloaded Atmel FLIP DFU programmer and installed the DFU drivers which installed without error.
I then load FLIP and successfully connected to the 16U2. I then uploaded the hex file from the Arduino folder and then unpluged and replugged the board.

Finally I reinstalled the UNO drivers. Sure a lot of work but it is fixed now.

Thank you for the follow-up.