according to the data sheet said" To configure the timer2 as a clock generator , bit C/T2 (in T2CON) must be clear and Bit T20e in T2MoD must be set, bit tr2(T2CoN.2) alse must be set to startthe timer.if you had make this timer 2 as a clock generator only , an interruped should never came out , but if you also used timer2 as a baud-rate generator simultaneously then when ever the uart interruped the clock output will idle,it's happened on my project,in my case i used this clock signal to monitor the uart port.so may not be the same as yours.
Chris Chang