It's not just you.
Many people have reported that their playlists are very slow to respond, or they get an empty list for up to five seconds on their DIRECTV DVRs.
This seems to boil down to a series of updates pushed out by DIRECTV in the last month or so. Obviously, there's something cooking under the surface there, although it's anyone's guess what it is. DIRECTV updates the software on its devices about every three months, sometimes faster if there is a "showstopper" bug found.
There isn't a whole lot you can do. Some people have reported that their DVRs are faster after rebooting twice in a row (reboot 2x within 30 minutes.) Some say that the problem goes away if you disconnect your DVR from the internet but obviously that's not a solution for the long term.
My contacts deep in the DIRECTV community tell me that the issue has been identified and that a fix will make it into a future update. Usually that means only a month or so, sometimes less, before the issue gets fixed. If their customer care team gets a lot of complaints, the fix could potentially get rolled out sooner.
So really the thing to do is sit and wait. That's not a lot of fun but that's what we're in for at this point. It's just a matter of sitting and being patient for a little while. I wish I had better news but... I don't.