I had been struggling with this problem for a long time and thanks to this thread I tried escaping the parentheses in (x86) and it worked. Thanks!
However I still cannot get another Run Service command to run. It is one that invokes FooBar itself from a right click on a filename in the FooBar library pane and enqueues the entire directory the file is in. It worked fine for me under XP, but I can't get it to work under Windows 7 x64. The command line I am using is this:
"C:\Program Files '('x86')'\foobar2000\foobar2000.exe" /playnow "$replace(%_path%,%_filename_ext%,)"
I have also tried using "$substr(%_path%,0,$strrchr(%_path%,''))" to get the path, but with no luck.
Any help would be appreciated. I really have spent a lot of time trying to get this to work because it comes in very handy.