when i try to load sketch to arduino uno version 3 shows error

Using Arduino IDE 1.x
1

when i try to load a sketch to arduino uno version 3 sametime shows this error and do not load it. :

Error: serial com is was being use by another program.

Anybody know what is happening?

Thanks in advance

2

Operating system?

Which version of the Arduino IDE?

What is the COM port number that you are using?

Do you mistakenly have multiple instances of the IDE running?

Have you re-booted you computer?