I sussed it out last night. The issue seemed to be the order in which I installed stuff. I uninstalled everything, then re-installed the oldest software first (ie, Gearbox) then everything else in chronological order, and installed the latest drivers last. No idea why it worked, but it did. Thanks for all the suggestions!
My laptop died and went back to the retailer. I've now got it back, but without any of the software that was previously installed. I'm re-installing all my Line 6 software, but when I open POD Farm 2.57 I get the following message: "POD Farm failed to initialise L6TWXY framework (code 0x8000e00a)" Laptop is an ASUS K55V with Windows 8.1 Has anyone got any idea what this means, what the problem is, and how to fix it? Thanks!