I have had that problem occur in the past week also. The minute I disconnect one of our employee's D800 from the docking station, the Dell screen comes up and it boots fine. She also said that she went away for a meeting and when she came back it was off and she couldn't turn it on. Even w/ all the peripherials removed, it would still cause the D800 to not boot. Eventually after locking and unlocking the dock it could boot connected to the docking station and all it's peripherials but sometimes it still prevents her from booting.

Everything else is fine and WinXP's system log shows no errors. Maybe it needs a BIOS update?

Finally had Dell replace my port replicator. Everything works great now.