FYI: We own a couple of Matrox APVe cards for our Nuendo Rigs. We use them for several years without any problem with triple 19" display, which gives a nice 3840x1024 resolution.
Since we wanted to upgrade to Win 7 64bit we found out there are no Win7 64bit driver for this card. However I found ‘XDDM64_209_00_158_se_u’ to work fine!
Herewith a link to the file: http://www.matrox.com/graphics/en/support/drivers/download/?id=380