Battery not recognized

I'm at my wits end on my wifes MacBook (4,1). I've replaced the battery with a NewerTech hi-capacity and I've replaced the battery connector. The only way I can get it to recognize the battery is to reset the PMU. However, this only works for a few days, and then again, I start getting the battery icon with an X. Reset the PMU, battery is recognized. Even when the battery isn't being recognized, if I disconnect the power, it will run off of the battery, just doesn't give any indication of how much charge is left. The only other thing I can think of is that the PRAM battery is bad or just the PMU is flaking out. Any other suggestions? Running 10.7.5