It happened three times recently. The first time I tried various buttons on the remote, including >> and >>|, and the movie jumped ahead about a minute after some fiddling. The second time trying various things didn't do anything (I think I tried to open the drawer, but I don't have a clear memory of it right now) and after waiting a bit I was able to power off the machine using the "POWER" control on the remote. The third time - and this is when I advanced the movie to the same location it happened in the second time just mentioned - I did nothing and the movie resumed eventually (30/45/60 seconds?) without intervention.
I can't recall this happening with regular DVDs on the BD-105 and I've played many more regular DVDs that DVD-Rs. The power button did work in the second example I gave so the player wasn't totally locked up. The first two discs in the set played without problem and I've played at least one other set of DVD-Rs from Warner Brothers without problem.
To summarize, I needed to restart the BD-105 one of the times, but it didn't require a power cord pull. Also, I don't know what would have happened if I just did nothing. In the future I'll give it several minutes before I try to intervene.
This appears to be disc read error recovery. The player is searching forward trying to find something it can read. Since you are not seeing the problem on commercially recorded shiny discs it would appear the player is having trouble reading your recorded DVD-R discs.
Where are you getting these Made On Demand discs? I play a fair number of DVD-R MODs as rentals from ClassicFlix and have not had any problems. But if you are getting discs at a store that are burned in a machine "while you wait", the machine producing those may be screwing up the disc writing process (burning at too high a speed for example).