Not with saving a single sheet, but,

having two different sheets open at the same time and then (happens often) when I try to save one of them - Adobe Reader 11 will crash.

It also sometimes crash with two or more sheets open, when I enter data into the form-fields on one sheet.

Other form-fillable sheets do not have this issue.

Can you please provide a BW version with white background?

There's a customised variant over there for as little as 25 KB. Rather simple compared to the magnificent artwork provided by FFG, but considerably less hungry for toner and ink.