When I try to open the xdl file in SSMS 2012, I get:

Failed to initialize deadlock control.

Key cannot be null.

Parameter name: key

When I try to open it in SSMS 2008 R2, I get:

Failed to initialize deadlock control.

There is an error in XML document (1, 2).

<deadlock xmlns="> was not expected.

Any help would be appreciated.