I think you'll be very happy with your purchase for years to come.
I've had mine (Mk I) for almost 10 years now and it's my most used lens. I also have the 4.0. I bought that for my wife thinking it would be easier for her to carry.
The 2.8 can be tiresome at the end of a long day...
This happens to the folks in my office quite a bit when they try to send attachments (usually pics) that are too large. I've always been able to fix it with one of two things:
1) Click "File" > "Work Offline"
Close Outlook
Re-open, then try deleting the message.
if that doesnt work...