Firstly there is still the bug from the original Elemental: War of Magic whereby holding down shift causes the mouse to jitter.
I had extreme difficulty in getting this to happen on my computer. In fact I couldn't reproduce this effect what so ever. I held down shift rotated the screen moved the mouse around for a good 10 minutes and couldn't get this to happen. How did you get this to occur?
edit: Ahhh it was the right shift that can cause this effect, but only after I rotated the screen while holding shift and moved the mouse around thereafter holding shift. If I did the same with the left shift it didn't reproduce the effect.
Once I let go of shift it returned to normal and I could hold either shift without jittering, have to rotate the screen to cause the effect. But it is very hard to notice the jitter even when it was happening.