Why this strange Windows 7 backup failure?

I don't understand why I'm getting this when trying to run the Windows backup tool.

An internal error has occured
The parameter is incorrect. (0x80070057)

Can you tell me what I should do about this error?

This knowledge base article (KB982736) suggests that the problem can be caused by having the decimal separator set to something other than .. It suggests two solutions:

• Change the symbol back to . in control panel > region and language > formats > additional settings
• or set HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\System\CopyFileBufferedSynchronousIo to DWORD value 1 using regedit.exe.

The KB article has more instructions on how to make the registry change.