So assuming it is a computer limitation and the ticket agent is unable to print one, or even if the agent is obstinate and refuses to print one, one idea I've had is to ask the agent for a security pass and let me run for it. My logic would be (at least to explain it to the ticket agent) that if I make it through security in time to run to the gate, I'll be able to get on the aircraft without the agent having to violate policy or otherwise stick their neck out for me. Do you think agents would be willing to go that route?

One thing I like about the Mac is the ability to print anything to a PDF file. I always print important documents and receipts to PDF files, which enables me to email them to be printed out, or in the worst case, emailed to my electronic fax service and printed at any fax machine. (I doubt TSA would accept a PDF copy of my BP on my laptop's screen, but there's another idea... ). I know there are similar solutions on PCs, but it's just so easy (and free!) on the Mac that I use that option all the time, and it's saved my bacon several times.