Itseems that on the newer platform, netfxperf.dll isn't a COM dll at all. Therefore, using regsvr32 on it isn't going to work. This can be verified using several techniques - checking the registry, running Dumpbin, using Dependency Walker among others.
I had this problem once as well. Windows seems to disable performance counters after a certain number of failures have occurred while trying to open them. I overrode this and never had a problem again by deleting the registry key.
Open regedit, and look under HKLM\SYSTEM\CurrentControlSet\Services.NET Data Provider for SqlServer\Performance. I can't recall the exact key name (DisablePerformanceCounters?), but its name will jump out at you as contributing to why it's disabled. Delete the key. I think it will take effect on the fly, but you may need to reboot.
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