I was probably in my junior year (maybe 8 years ago) when this little gem occurred.
I thought I had all of my tuition taken care of through scholarships and loans and whatnot. I even had a "receipt" that said my total due was $0 at the beginning of the semester. About 2 - 2.5 months into the semester, I get a bill for a touch over $700. Turns out the bursar's office made a *tiny* miscalculation and then sat on it for a while.
I freaked the crap out when I got my overdue notice (which was also the first time I was contacted about it) because I thought I had everything squared away. I had enough money to cover it at the beginning of the semester, but I decided to prepay stuff like my rent (because I was trying to be responsible and budget my money for the entire semester). So when they got around to asking me to pay for it, I had nothing.
I called them up about it and they absolutely refused to work with me on it. I couldn't even get an answer as to why it took so long to get this to me. No one apologized or could even offer a reasonable explanation. One lady even got really rude and spat out "What do you want me to do about it?" I'm pretty sure I was on the verge of tears at that point and just hung up on her.
After that, I emailed the entire situation to the Bursar himself, but just got a reply along the lines of "This is what you owe. Pay it or you will get an encumbrance." There wasn't anyone higher on the ladder I could go to (except maybe the President).
Luckily I worked for an awesome place on campus and they referred me to some awesome financial aid people who sniffed around and found a little extra money that covered most of it. So, it turned out all right in the end, but I'm still a bit miffed that they just let it float around for so long and didn't even begin to apologize for any of their ridiculousness.