Comfortmaker RPJ 2 problems

[macman4]

I have a confortmaker rpj 2 gas furnace.My furnace turns on O.K but after awhile, as it heats up I hear a clicking sound. It happens most when ther is a big jump in tempurture range. For instance i have it set at 68 at night and to turn on to 72 in the morning. At the end of the cycle {72} is when i here the clicking noise. It will click a bunch of times then shut off then restart again. I had a problem like this before and had heating guys fix it. They cleaned the little window below the glow plug. This window had, of all things lady bugs on it. This time I took it out and cleaned it. But still doing the clicking noise and turning off and restarting again. Sorry about the long post, but wanted to explain best I could,
Thanks, Bob McDuff

[GeeWhiz]

My Comfortmaker furnace is a model GNJ075N12A1. It is about 8 years old. It is not a "high efficiency" model, but it has a combustion blower motor/fan or sometimes called "inducer fan" that assists the exhaust out the flue pipe.
Recently it does this same exact thing, especially after a lengthy cycle of heating up. At first I thought it was a particle or fragment that was caught in the fan wheel, but now I'm not sure. It is a fairly rapid, uneven clicking noise--like you described.
I described the sound to a furnace repairman, and he thought that maybe the "high limit cutout" switch was activating and shutting the furnace down.
Macman4, did you ever find out what caused this problem in your furnace?
Thanks,
Quent