I had this same issue. I can't remember where, but I found this little work-around:
1. Open an elevated command prompt (on the Start menu, search for 'cmd', right-click, and Run as Administrator)
2. In the command prompt, switch to your optical drive (probably 'D:')
3. Type 'cd "Boot Camp\Drivers\Apple" and hit enter
4. Type 'msiexec /i BootCamp64.msi' and hit enter
Obviously, all of that typed stuff should be without the single quotes, though the double quotes in step 3 are necessary. After hitting enter in step 4, Boot Camp and driver setup should go normally.
I've been using Windows 7 Professional 64-bit since release on my Aluminum non-Pro MacBook 2.4 ghz with no problems.