I had problems with my A/C in that it would shoot out a few ice chips (literally) and then die. Very soon thereafter it just blew warm air all the time. I made FOUR trips to the dealership.
Trip 1: Replaced evaporator core - lasted three weeks and then blew warm air
Trip 2: Replaced condensor - lasted two weeks and then blew warm air
Trip 3. Replaced compressor - don't know how long it lasted, as it was done in November and was cold the next week. Warm air (of course) when I fired it up for the first time this spring.
Trip 4. Replaced ALL lines, including some ridiculously hard-to-reach lines that they resorted to using crowbars for. Ugly to watch. Blowing cold air for now, but the last visit was only about ten days ago. Fun!
He told me that he definitely found leaks around the hoses this last time. Used the dye and black lights as per Doug's suggestion. The leaks were hard to trace because they were so far back on the line. My bet is that it could be your problem.
Good luck, and let us know what you find!
Chris