Object reference not set to an instance of an object.

Hi Folks,
So it's been 5 days since i'v been trying to get my perfectly locally-working website to work online.
First i went thru the virtual directory settings prob.
Then i went thru working around medium trust level (took most of the time).
When i got that one done with, now i'm having this error pointing to something wrong in my custom membershipProvider :
Parser Error Message: Object reference not set to an instance of an object.

Source Error:

Line 84: <providers>
Line 85: <clear/>
Line 86: <add name="HDIMembershipProvider" type="HDI.AspNet.Membership.HDIMembershipProvider" connectionStringName="HDIConnectionString" enablePasswordRetriev ...