Usually this issue is a result of some calculation that is just too much for QlikView or the result is "not calculable" within your parameters. You might have either a standard expression, calculated dimension or formatting expression that is causing an issue. The thing that bothers me about your question is that you are simply disabling expressions. I would not think that would cause an issue usually unless you have some other expression that refers to the expression you are disabling.
I have a "conditional" error "Allocated memory exceeded" in Pivot (with 2 dimensions one of which is calculatable):
1. In Access Point - it does not appear when all dimensions are in rows and appears right after dragging of the calculated dimension from rows to columns
2. In QV Desktop - it does not appear at all
...believe you or not. Thinking how to avoid such a displaying, namely change the wishful view to something else without lost of representation.
I had this issue when i develop trend analysis. I had written some expression in the dimension which was given this memory exceed error, then i brought this expression in query itself to avoid this error and it worked fine. I would suggest you to bring your dimension calculation in query itself to avoid this issue.
I had a similar problem with a very small table - 392 rows by 10 columns, so no way that memory was exceeded on my 16GBRAM machine!
However, Raju is on to something - my last dimension was calculated and would not display in a pivot table ("allocated memory exceeded") but would display fine in a straight table. I took Raju's suggestion, and moved the 'mixmatch' function into the script. Bingo! The pivot table now displays without issue.