Shortly after returning from Interaction in 2005, I took stock of the bills that we ran up on the trip and concluded that I simply did not have enough money to cover the expenses run up on the Worldcon trip. I was obliged to take a loan from my 401(k) retirement plan to meet current obligations. I've been paying $100/week out of my paycheck since late September 2005 toward that loan. Yesterday's paycheck had a deduction of only $63.46, which means that I've paid off the loan. Hooray!
Mind you, I rather expect that I'll have to do this again in October 2007.