[Litecoin] Issues mining

Hello folks.

I'm pretty new at bitcoin. I have searched for a bit and found out that litecoins are the best thing to start. So I joined pool-x.

I have three computers: a Pentium III Mobile one, which is happily mining at 0.48 kH/s.
My main laptop, a Sandy Bridge i7 with Nvidia GTX485M graphics.
And a netbook I bring to class (and therefore free power), an AMD V105 with an ATI HD4225.

Pool-x seems to recommend either ScryptMiner GUI or Reaper for CPU/GPU mining.

ScryptMiner works well, 0.48 kH/s (1 thread) on my PIII, ~24 kH/s (8 threads total) on my i7.

But I haven't been able to get Reaper to work on my i7 laptop or netbook:
- on my i7 laptop, the hash count skyrockets to 10 GH/s (!!!) for 15 seconds before freezing my system. Latest Nvidia Verde drivers installed. Setting aggression to 10 does the same thing.
- on my netbook, it receives longpolls and the program seems to be running but doing nothing, sitting at 0 kH/s constantly. The latest drivers and the OpenCL SDK is installed.

I guess I would be able to get more litecoins by using the GPU, but I can't seem to get it working.

Any help?