First thing to check if you have a leak:
1. There is a weep hole mounted to the back near the 12-cup mark. If you use something other than the carafe to fill the water reservoir it may leak. Those who brew full pots are more likely to experience this particular issue.
2. If you are measuring the water correctly and it still leaks, here is the advice from Mr. Coffee:
There is a small rubber tube that goes into the back of your coffee maker. Please carefully remove that rubber piece, by gently pulling it out of the back of the coffee maker.
Look very carefully at that rubber tube. There is a hole in the end that was inside the coffee maker.
That hole is supposed to be facing down. If you replace the tube, by carefully pushing it in, making sure that the hole is facing down, it should correct the issue with it leaking.
3. If it is leaking from the bottom (not from the brew basket area), it may be that one of the two tube attachments directly above the flat portion of the bottom has come loose. If your unit is out of warranty, you can partially disassemble the coffee maker while unplugged to check (this is not something recommended in the owner's manual but is an endeavor you take at your own risk). If either tube comes off or perforates, it could result in a leak that would appear to puddle at the bottom (without drips down the sides).
4. If it is leaking from the brew basket area, it may be that:
* the decanter is not fully seated;
* you have removed the carafe for over 30 seconds, which is the maximum time specified by the owner's manual during Pause 'n Serve;
* the permanent filter is clogged or worn out, which may cause the water entering the basket to build up faster than it can exit;
* another source of potential overflow stems from using the wrong size or placement of paper filter, either of which may cause the paper sides to collapse in on themselves thereby impeding direct water flow to the grounds;
* the paper or permanent filter has been filled with fine grinds. The user manual recommends medium grind, which is the standard recommendation for most automatic-drip coffeemakers;
* the water filtration disk has been removed, is clogged or has worn out;
* the filter/brew basket assembly isn't seated properly.
5. If you cannot brew at the rate of one cup per minute, which is the Good Housekeeping Institute recommendation for modern automatic-drip coffee makers, it may be possible to restore it with a good cleaning. Oftentimes a single de-scaling procedure is not enough, even if the red cleaning light goes out after one go around. Repeat the cleaning procedure three or four times, and time the dispensing rate (10 cups should take 10 minutes, etc.). Oftentimes this procedure will also improve flavor by removing rancid oils and stray coffee grounds.
6. While it is difficult to determine whether brew temperatures are reaching the ideal range of roughly 190-205, you may, however, measure the temperature of the rinse water after cleaning the coffee maker with vinegar. In a pre-warmed mug you should get a reading of 170 according to the Good Housekeeping Institute. My experience with this coffee maker after two years of use is that freshly brewed coffee comes out cooler than rinse water does - more like 160.
7. If the coffee tastes bad, turn down the warming plate. Overcooked coffee will smell and taste burnt. Likewise, coffee brewed on the "strong" setting may not be to everyone's liking.
8. For best possible flavor, store fresh, whole beans in a cool, airtight container. Grind the beans using a burr grinder, and use up the resulting grind within 30 minutes.
9. Last but not least, don't forget to keep your original receipt and box. If the above suggestions do not work, you may need them!
While some of these tips may seem all-too obvious, I hope there is at least one suggestion in here that helps someone achieve better results. I am convinced there are a lot of lemons out there, but despite all the bad reviews I bought one of these coffee makers at Costco over two years ago and had no problem with it (other than the bad coffee flavor that I began to get after spent grounds backwashed into the water reservoir). It overflowed only once in that time, and the Pause 'n Serve worked more reliably than any of the other machines I own. The main complaint I have is that the nonstick warming plate still rusted, but I discovered that it was caused by putting a damp decanter fresh from the dishwasher back in place.