I managed to get it working!
I reinstalled drivers for my phone (I think the problem was one type was missing or something?) from PDAnet from here,
Download PdaNet . I followed the program, but when I got to the 'reinstalling drivers' part (when you plug in your phone and your computer searches for drivers), one failed to install. I think this is common with Windows 7?
To fix this, I went on start, and typed Devices and Printers, and pressed enter. It showed my Android device with an orange triangle. You right click, go on Properties, Hardware, Change Settings, and on the Driver tab click Update Driver. It should be able to find the right driver from the PDAnet if you click the search for drivers and finish installing without failing.
Then PDAnet finished whatever it was doing, and when I opened up SuperOneClick again, and it didn't freeze! I plugged in my phone (with USB debugging enabled) and it rooted it, no problems

Hopefully this will help if anyone encounters the same problem.