avrdude: ser_open(): can't set com-state for "\\.\COM3"

My arduino uno was working fine, I put it away, and I got back out, and whenever I try to upload something I get this error message.

avrdude: ser_open(): can't set com-state for "\.\COM3"
An error occurred while uploading the sketch

Please help me

What does device manager say; is the Arduino recognised? Is COM3 is indeed the Arduino?