The Trouble With Potty Training

Okay, fellow Mommies I am at wits end with Miss Aislynn the last two weeks and I am in desperate need of advice. We potty trained her starting about 18 months and it took some work, but we got there about 6 months later. She's had her little accidents here and there since, usually following a weekend not at home, but nothing we haven't been able to handle. But since last weekend we've had multiple accidents every day. We've tried everything I can think of, we've punished her by grounding her, sending her to time out, cold showers (not too cold with the temps we've been having) and we've tried positive reinforcement. We've offered treats, stickers, calm talks and the latest being a Princess Party after a month of no accidents. We still have had no luck and my patience & sanity are wearing thin! Does anyone have any suggestions or ideas on what to do & what it might be causing it?