I apologize in advance if I've missed something that should be obvious, but this one's making me crazy.  I have an LM1972 uPOT on +/-5V rails feeding a TL072 on +/-12V rails wired as a unity gain buffer as per the LM1972 datasheet.  I've used this circuit for years with a linear power supply without any problems, but when the circuit was ported to a system with a (noisier) switching power supply, the TL072 would latch up after only a few hours of operation .  First problem: I had put the TL072 on +/-5V rails without consulting its spec sheet (too low, as it turns out), so I substituted the more forgiving LF353.  The latch-up condition would still occur after several hours of operation.  I then replaced the 353 and raised the rails to +/-12V as they had been in the functioning legacy system.  No dice: the latch-up still occurs.  Besides power supply noise, the only other difference between the functioning legacy circuit and the faulty new one is the impedance they're each loo!
 king into: 2.7k for the former; 22k for the latter.  Does anyone have any ideas about what might be causing the op amp to latch up?

Many thanks,
RR       
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