This week, we had an issue with Excel files opening slowly on the network. Some, despite being only 21K over 1000BT, took as much as 5 minutes to open. They opened fine locally.
Someone beat me to posting this on one of the sister sites, but since there are so many fellow system admins here, and I don't see it here also, I thought I would post the question and answer here too. I am sure I will save someone some time.