Sorry for the delay in answering, I was out of town a few days, followed by having to learn for some heavy exams..
Anyway, this is what I've come to:
- tried all the solutions provided, none worked
- reinstalled on my comp, after clean boot (Ati Radeon HD4870)
- installed on an equally new computer (Ati Radeon HD2600XT): same glitch
- installed on a somewhat older computer (Ati Radeon 9800XT): still same glitch
- installed on my original computer from when I bought the game (NVidia GeForce2MX): NO GLITCH!!
So, it clearly isn't the disc that's damaged.. It must be somewhere in the software. All systems work on DirectX 9.0c, but the oldest system works on Windows 2000, as opposed to the other systems that use XP (all 32bits). So it could be various things...
The old computer is, alas, not powerfull enough to nicely play the game, so I just passed the one jump, and exported my savegame to my new system, from where I could continue without problem. As a sidenote: after exporting the savegame, I could make the jump, and the jump back without a problem... Which I really can't explain. What was different to the gamefiles once I had imported a savegame?
In any case, I have finally finished URU (after all these years... kind of ashamed), and I'm waiting until x-mas passes to order a Collector's Edition, to play the Path of the Shell too (and have the soundtrack ). I'll post a reply whether the expansion by itself solves the problem as well..
Greetings, and many thanks for taking the time to help me!