Mine does a very similar thing. It will sometimes run for 30 min. before blinking, and sometimes will only run for a few seconds. Sometimes, instead of running, the features that are enabled (lit LED on Hi-temp wash, for example) will clear (LED no longer lit) and nothing happens, as if the board reset.

When I killed and restored the power to the dishwasher the same three lights blink.

All of this tells me (and I'm absolutely no expert, so take this with a few grains of salt) that the control board is going bad. I took mine out and searched for the part number (154568401, that's from memory but looks right as I search for it again) but nobody seems to have any available. Some claim to have replacement parts that should work, but I haven't spent the time talking to them yet.

It's probably worth calling and talking to one of the Frigidaire authorized parts dealers, maybe they have an idea. Frigidaire's customer support section on their site has a tool for looking up local authorized parts dealers.