Does it work if you do it on the command line?
Does it work if you execute it as the system account using PSExec?
Try running a single command using powershell to write to a log file and see if that works, and work your way up from there.
This works for me on both 32bit and 64bit machines:
waithidden "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe" -ExecutionPolicy Bypass -command "get-help | out-file C:\windows\temp\test_powershell.txt"
Here is a task I created to test powershell and report the major version through the exit code: http://bigfix.me/fixlet/details/5019