[THIN] OT: HP TCs as IE kiosks

we have a bunch of HP T5270 TCs being used for IE kiosks to our timesheet system (Deltek). They;re trying to upgrade to a newer version of Deltek (I know nothing about it) and IE6 on the TCs just won't work with it. You get the logon screen and after entering your credentials you get the "cannot find server or DNS error" message  - same web server.

from IE on a WinXP PC it works fine.

any ideas or insights as to how embedded XP might be a tad different?