wlanapi - WlanSetProfileEapXmlUserData

I'm trying to use the wlanapi that comes with WinXp sp2. I'm facing a
problem invoking the method WlanSetProfileEapXmlUserData. The fifth
parameter its a pointer to an xml file with the credential settings.
I've checked the online documentation and I've used the samples that I
found on msdn but I always receive an error (1206). I read also that
people is facing the same problem and we haven't found a solution. I'll
appreciate any help cause this is driving me crazy.
Thanks,
Nelson