Have you tried reflashing the PICkit2 using the ISCP connector on the inside, using another programmer?
I have had a PICkit2 delivered with no operating system that needed that to get it going. That was a long time ago when Microchip managed to ship a batch with no OS.
More relevantly, I've had PICkit2 programmers randomly loose their OS, and refuse to reflash via USB. In the thousands of times that I have used PICkit2s, I've had that happen 10 times or so, and each time I've just reprogrammed the PICkit2 using another one and ISCP.
The only other fault that I have had was when there was an earth voltage difference between the target circuit, and the PC that was running the PICkit2. That blew one of the SOT23 transistors that allows the 12 V for programming to get to the target PIC.
If you can programme the 18F2550 inside the PICkit2 using ISCP, then the 18F2550 is almost certainly fine. If that works, I suggest that you turn on the USART tool. If you link pins 4 and 5 of the PICkit2, you will get anything sent by the USART tool echoed, and no echo without the link. If that works, pins 4 and 5 are probably fine. You can also test the supply voltage on pin 2, where pin 3 is ground, to check that the voltage out is as required. Pin 1 is the Vpp pin, so that goes to 12V when programming. You will need to tell the PC that you are using a PIC that needs 12 V to programme.