Diesel Bombers - Pushed Valve Seals...?

Not too long ago my valve cover gaskets started blowing by, especially on the No.6 cover, wetting my head and spraying oily residue on the firewall. I pulled the covers off and noticed that ALL of the valve seals were pushed out and just hanging out up in the valve springs. Has anyone had this happen or have any idea why it might have?

The head was completely reworked about 5,000 miles ago and was broken in fairly gently (especially condsidering my typical driving style :ouch:). Boost hasn't been over 35 psi, studs have been properly torqued and retorqued as suggested, blowby out of the tube and dipstick are minimal...

I plan on checking and replacing the seals when I tear down the motor (again...:argh:) and transmission, but I would like to know what might have caused the seals to push out. Any help would be appreciated. Thanks!