Came home from working away for past 4 weeks late tonight. Forgot to remotely lower my central AC temp. Wouldn't have mattered anyways, because the batteries to the thermostat went dead 10 days ago. Put new batteries in and the unit still didn't seem to come on. 3 sweaty hours later, with the temp coming down from 85 to 83, the lightbulb goes off in my head, to check and see if the condensation drip pan got full and triggered the safety shut off for the unit. You bet. Tired me is somewhat ashamed that I didn't check that sooner. Now (very) slowly cooling off me is thanking the Big Guy that I had a wet vac that I just so happened to purchase the day before I left.
Only got rid of the water under the unit, I'll worry about the apparently clogged drain once I wake up from much needed rest.
Had same trouble last year and bought one of those test tube cleaner brushes (narrow - don't get the fat one as it has trouble with the pipe bends) and got rid of the gunk that was clogging the pipe.