multiple displays potrait mode trouble

Searching for the best size mate to flank my 2405wfp I chose the 1707fp in portrait mode. The width dimension is the closest I could find to the height dimension of the 2405 , I bought one for each side of the 2405. Current display adapter is the x300 that came with my Dell dimension 9100. My intent was to buy a second video card to run the two 1707s but I stumbled on this problem while experimenting with one 1707 hooked up to my existing card on the second head (VGA). One application I use is a drafting/ modeling program that uses open gl to render 3-d models. In portrait mode the program will not render. I tried portrait mode on the 2405 (connected to the DVI head) and it will not render either.  In landscape mode no problems using either monitor. My question is: would this be a display adapter issue that could be resolved with a certain adapter to run the portrait mode monitors, or is this an issue with portrait mode in itself. I am very happy with the match up of these monitors in this configuation otherwise  but if I must run all 3 in lanscape mode I will have to return the 17s and look into something else that will get close to the height of the 2405. Thanks for any help.