Still awaiting some feedback from support around this, so had a quick look on the location in question to see whether this has somehow resolved itself & thought I'd share my findings..
Logged in > opened the Recorder to replay a transaction & interestingly, works fine (on the web ui shows as a failure).
Anyway.. when exiting out of this, I get an "Interactive Services Detection" dialog appear (see screenshot below) & when I 'view the message' I got a browser window with the standard 'page cannot be displayed' message...
Closing the browser then gets' me the second part of the screenshot... I tried to copy out the details, no luck, but reviewing them it does seem associated to the SEUM function. Clicking continue then just closes all this down & brings me back to the desktop.
Unusual behaviour to say the least. Perhaps because it's Halloween??