I had a very weird problem last night when printing.
i'd been printing for about 10 hours. with the printer plugged into a laptop.
the printer randomly shut down, there was also a strange behaviour in that the printer would appear to come on then go off immediately, then seem to come on, then go off, so the lights were flashing!
Had a look at the board on the back and the 7805 regulator on the board was roasting hot. (burned me to touch it) I wet my finger and touched it and it sizzled.
I removed the 7805 regulator from the board and the printer has been working fine ever since.
I've looked at the rep-rap pages, this is actually a known issue, when the printer is connected to a PC so 5v is sourced by the USB supply, and the 7805 is also installed, differences in the supply voltages can cause the 7805 to run hot/overheat/shutdown and break.
I have no idea if using the panelolu exacerbated the problem as the 5v supply would be more loaded.
the solution to this will certainly involve a new regulator for my machine and as a proper fix a switch for selecting between USB power and machine power for the 5v (or a dedicated USB lead when I've cut the power lines leaving on the data lines intact)
so not supply trouble but certainly board based power issues.