I thought I'd seen all the Outlook prompts possible, but when I saw this one and it sat there for 30 secs or more, I had to hit "Prnt Scrn" to capture it. I've absolutely never seen this one before. Admittedly, my machine was running a couple of Virtual Machines at the time, so was a little on the slow side. This was seen when opening a folder in a PST file for the first time, although I'd already copied a number of items into it. Another instance of learning something new every day ;)
Whenever my machine is CPU-busy, and I go to bring Outlook out of the system tray, it pops up and tells me it can't talk to the exchange server. Huh? I really wish they'd fix this bug..