I'm running 4.0.12, and have the same problem. My local e-smith guru checked for me, and said
"the rpm command gave a bunch of errors that indicate files are missing.
Guess what - they seem to be e-smith webpanel files
"
On any other webpanel link, the 'please wait' comes up, then the page comes up fine. On the backup/restore link, the 'please wait' comes up, then stays until timeout, just like Barry Rogers' problem (from what I gather).
I have done no tinkering/customising to the webpanel (in fact, very little to the whole installation really)
Cheers,
Greg.