I have a 2008 Mac Pro, see specs in my signature below and everything works perfect for me. There is little technical information to go on and it could be a number of things causing your issues. As to steering clear of Apple/Macs that is a complete falsehood and it all comes down to simply computer hardware and software regardless of what you use. You can duel-boot your Mac Pro like I do and use a dedicated hard drive for each OS.

All the programs mentioned work just fine for me both on Windows 7 Ultimate 64 bit and Mac Snow Leopard 10.6.4 64 bit with no problems (except of course the reported bugs in software like Vue, C4D, etc.)

I use: Poser Pro 7, Poser Pro 2010, Vue 8.5 Windows, Vue 8.5 Mac 64 bit (not very stable at this point still beta), C4D and ZBrush 4.0 without trouble.

Hope things work out for you.

Jeff

Development on: Mac Pro 2008, Duel-Boot OS - Snow Leopard 10.6.6 & Windows 7 Ultimate 64bit, 2 x 2.8 GHz Quad-Core Intel Xeon , 10GB 800 MHz DDR2 RAM, NVIDIA GeForce 8800GT.