This is usually a signal or a hard drive problem.
Please post your signal readings from at least 2 tuners and all sats or take pictures and post them to a picture sharing site and post the link here.
To test the hard drive run the BIST test below.
* Reboot DVR via red button inside card door.
* When you see "Running receiver self-check" press select
* You will see "Entering Diagnostics Mode..."
* Select Advanced Tests Menu -> Hard Drive utilities -> Short Smart test
You can also run the file test, and the DVR can sometimes repair a bad file report.
* If the other tests pass, run the surface test. Warning: This process could take several hours to complete. You may want to run it overnight.
The good news is that every attempt is made to save programming. This is less destructive than a reformat all and could provide you with a more stable system if you are having problems that appear to be related to the hard drive.