I don't remember the exact limit, but it was just over 2Gb, IIRC, so you are probably correct.
I-deas is a 32-bit app and as such, cannot address more than ~2Gb in memory. When your MF files are near that, it's likely trying to load at least that much and thus you hit a problem.
Not sure if older posting on GTAC might have tips to handle it, but they they basically boil down, as you might guess, to dealing with smaller chucks of data at a time.
Good luck.
Pat McManus
Siemens PLM