From the experiences I've had with my Keg, the reflash can take anywhere up to an hour, although it can be as quick as 15 minutes. And on some occasions, I think a reflash worked when it wanted to (usually disconnecting the Keg and re-connecting it fixed it). But other boxes will no doubt vary in behaviour!
To be sure it's not doing a firmware upgrade, use the tools to 'Repair DMS (PHTSYS)' - go back to the car and see where you are at.
Also, make sure that you have some music on the DMS too - using your software of choice!
If you are still not getting any sense out of it, then we'll go a bit more advanced to finding out what's going on....