Apex 4.2  200 Page Items limit

Hi,
I have a master-detail form which was getting close to the 100 items per page limit in Apex 4.0 which I then scaled back and got to work properly. I had thought that I could start adding more columns to the detail part of the form since 4.2 was supposed to have increased that limit. I am finding that this does not seem to be true at least in the case of this particular form. I tried increasing and started getting 404 errors when trying to save data--same symptom I had had with 4.0. I am back nearly to the same # of columns I started with--and nowhere near the 200 limit. Columns are month by month projection data that I had hoped to extend with the increased page item limit.

Am I missing something required to take advantage of larger page items limit? Do I need to use one of the new templates?

Any pointers would be appreciated!!

Pat