Does that do something different than just shutting the box off ?
It can cause some errors on the hard drive, theoretically damaging it. I find that sometimes if I put the STB on standby while a recording is taking place the same sort of problem happens. Other times, I still have weird issues with recording, possibly due to something odd inside a feed? Anyway the usual message I receive is an "Limit Error: CAN not record" or something along those lines. The only fix I found for that is the following (using Windows, that is. I'm a Linux newbie, so still learning there):
1. Properly disconnect the drive from the STB through the menu screens.
2. Connect the drive to your computer and wait for your PC to recognize the drive.
3. Right click on the drive and select "Properties" from the drop down menu.
4. Select the "Tools" Tab in the dialogue box.
5. Under "Error-checking," click Check Now. You want to Automatically fix file system errors. I don't usually ask for a recovery of bad sectors.
6. After this is complete (usually in a few minutes), select "Defragmentation." Select the drive and click "Analyze disk." This could take just a few seconds up to quite a few minutes depending on the size of the drive and the last time you defragged it. If you get a 0% fragmentation, you can skip step #7.
7. If there is even a one percent fragmentation found after the analysis, I click on "Defragment Disk." Again, time can vary from a few minutes up to a couple of hours.
8. After this, be sure to disconnect the drive correctly with the proper "Safely remove hardware" menus for USB devices, and reconnect to your STB.
This, I have found, generally saves me from sudden headaches when the drive doesn't want to record a program. I'm using a WD 1TB external drive with its own power source.