Whilst Tech is right in it doesn't get send/uploaded until the next update as I mentioned in an earlier post, I think he missed the bit about nothing happened when you clicked the Email to Alwil software, yet when you did this for others the submission window popped-up. So it isn't an issue of it not being sent but being unable to even get that far.
Have you opened the Infected Files section and are you right clicking on the file concerned I think not. Though you comment on being able to at least get the mail window suggests otherwise, were these other files in the Infected Files section ?
Was this the window that popped-up, see image ?
If you just click File, Email to Alwil software, nothing will happen (I just tried it) as nothing has been selected to be emailed/submitted.
I don't know on the off chance it might have anything to do with the file size, there is a setting, Program Settings, Chest, Maximum size to send, try adjusting that to cater for the size of the file you want to submit.