An unidentified air carrier aircraft suffered a malfunctioning pressurization system allowing the cabin to climb to 14;500 FT while the flight crew conducted an emergency descent. The flight diverted and landed safely.

Narrative

We were at FL380; seat-belt sign off; and a cabin altitude of approximately 6;000 FT when the pressurization had a rate of climb increase to approximately 1;500 FPM and climbed the cabin altitude to 6;100 FT. This lasted approximately 15-30 seconds. The pressure bump came back down to zero and the cabin altitude returned to 6;000 FT. Then; less than a minute later; the same scenario recurred.The Captain and I agreed this was not normal and started discussing a descent. Less than 30 seconds after the second event the cabin rate of climb increased beyond 1;500 FPM and continued to climb. The Captain requested initially FL340 to see if it would improve the situation; it did not. The cabin altitude continued to climb and the Captain and I agreed to an emergency descent. The Captain declared an emergency and the emergency descent was initiated. FL240 was issued from ATC and eventually 11;000 FT.On the descent; the cabin altitude climbed and limited at 14;500 FT. Upon reaching the high teens; the cabin started to descend below 14;500 and eventually started to work normally. We diverted to a nearby airport and landed with CFR following us to the gate in case of injuries (no injuries reported) and completed the flight.