What he's suggesting is kinda what I have been saying.. You've not gone through all the other possibilities which could be causing your blank page for only TWO categories..
Logically if IH2 was the cause you would truly have issues with more than just two categories.. A quick look at the IH2 code and you would see that it is indeed category neutral.. I suggest having a go at some of the troubleshooting options suggested in the article nagelkruid posted..
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