Another issue I ran into in IE 8, regarding the Siebel 8.1 Mobile client. This issue was reproduceable on both debug and non-debug modes.
After the mobile client opened up fine, none of the menu items inside the UI framework would open. The menu items at each applet would not drop down, and even the Help->About View would not open up.
At first I thought the pop-up blockers were playing spoilsport again, but the problem persisted even after pop-up blockers were turned off.
Then , a colleague suggested making a change to the client CFG file. In my case, it was scomms.cfg.
1) Open the client CFG file.
2) Find this line :
EnableFQDN = FALSE
3) Change it to :
EnableFQDN = TRUE
And that fixed the problem !! I don't know what FQDN has to do with menu items, maybe its something wrong with the UI framework.