Backend admin issues

[Ironman28]

Many admin functions such as trying to change an e-mail address (or delete a user, etc.) generates a 503 Mediation Guru error message, even though the system correctly makes the change -- here is the error message received:
Error 503 Service Unavailable
Service Unavailable
Guru Meditation:
XID: 571662841
Varnish cache server

[ahelme]

Steve - can you add some more details on exactly what gives an error?

URLs would be good, and exact steps that produced the error.