Zoom In Slow-down fix

I had a problem (in C6 and 6.02) where, if i zoom in more than about halfway, my whole UI becomes very slow. eg. 2 secs to perform another zoom step, or a nudge.

I fixed it as follows . . .
Open the “Quantize Panel”
Click on the Preset pull-down.
Choose “Restore Factory Presets”

I had created a Quantize preset of 1/128 127-let, which i use for very small nudges.
Seems this was causing problems.

I like use Nudge, via keyboard shortcuts, to move events in very small increments without the clumsiness of dragging.
What is the smallest Nudge i can create? How?

Also, now the grid lines are not visible through transparent events (grr), has anyone got a good tip for aligning an event to the grid using small increments, via the keyboard?