I have been having this issue in my Lightroom 4.1.
This is how to duplicate the problem:
Select an image and use the Adjustment Brush.
As an example, select Shadow and enter a value, say 10
Try scrolling the mouse button back and forth.
Normally, LightRoom would crash after doing this. If it is not doing the same on your PC, then I guess the issue is isolated to my PC only.
Bug on Lightroom 4.1 Adjustment Brush
Its not about selecting adjustment brush or scrolling down. Adobe Lightroom 4.1 has a bug, it cannot handle huge processing.
Normally it does not crashes that easily but may be it depends on your processor speed. I personally switched to version 3 as it was impossible to work with 4.1. Adobe launched RC2 to deal with the problem but the RC2 still crashes just like RC1.
If you want to work on 4.1 then I suggest that you uninstall CS6 (if you have installed it).
This solves the problem for some.
Turn FTP off, that also works for some.
It is rumored that Adobe will soon launch RC3 which will be a complete copy except for this bug. 🙂