Isn't there an unstack selection when you Mtext? I am out of the country and I don't have my ACAD w/ me however I think you can unstack if you highlight the value and right click on the highlighted value and keep it unstack ubtil you reverse your selection.
There are several options for fixing this one at a time but I'm trying to fix many drawings with lots of stacked fractions in MText in each. I'll try StripMText from lpseifert and report back. Thanks all!!!