All I've found on it is
12/11/2006: 1318 Software Version P3.64 for DVR501/508/510
Effective Tuesday, December 12th, Engineering plans to spool a PARTIAL PHASE of software version P3.64 for the DVR501/508/510 receiver. This is primarily a non-forced maintenance release available at ALL satellite locations.
At this time P3.63 and P3.64 will be the valid software versions for the DVR501/508/510.
Also found this, from last week
12/06/2006: 1103 Software Version P3.64 for DVR501/508/510
Effective Thursday, December 7th, Engineering plans to spool a PARTIAL PHASE of software version P3.64 for the DVR501/508/510 receiver. This is primarily a non-forced maintenance release available at ALL satellite locations.
At this time P3.63 and P3.64 will be the valid software versions for the DVR501/508/510
so did they find a issue or something to back out of the update?