Digital ballasts and generators

Power outages are not uncommon around the area I live. A couple winters back, for example, a particular storm resulted in loss of electricity for several days here but up to a week in other locations. As you could imagine, this sort of complication when growing your own makes having a back-up generator an extra important necessity.
Those times that the power has gone out we've managed to use the generator to run our old magnetic ballasted lights. Recently I decided to purchase a Lumatek digital ballast and have read simply that they shouldn't be powered by generator.

No other details were given and it seemed pretty vague to me. Before I contact the manufacturer or anything I was hoping somebody here might have some experience or insight regarding this. Perhaps this just means they shouldn't be powered by a generator/plugged into one directly or via extension cords?

Our generator is gasoline powered. The current runs into an EG Switch, which allows the house to be powered via existing wiring. In the event of an outage we have to do everything manually. The cord must be plugged into the EGS box, grid power turned off, and the generator started manually. After everything is situated we get power thru existing outlets, so lights would not have to be replugged into any extension cords or anything like that.

I have magnetic and digital ballasts and I've never had a problem running them on my generator (average twice a year, for 4-12 hours each time). I don't have an autostart, so I run my stuff through a UPS for computers, which keeps it all running for about 30 min (plenty of time to get the gen fired up). The UPS also has an alarm to wake me up if the power goes out at night. The UPS basically charges a battery constantly, and all draw is from that battery, so it's possible this is why the digital ballasts do OK, I don't think I've ever tried running the lights directly off the generator. Generators are very common on large reef aquariums though, and almost all of them are running 250-400w MH's, and I've never heard of an issue using them with electronic ballasts before...