Do you get the same problem using Windows run command, located at Start - Run?
If so, then this is a Microsoft problem, not mIRC
If you'd like to upload the screenshot, the host I use is ImageShack
. You don't need an account to host there, but if you create one (and it's free), then any pictures that you host will be stored in your account and you can make the pictures either private or public (on a picture by picture basis).