I must admit I had problems with it too - so much so I now replace + with #= which Excel seems to have no problem recognising the replacement as text.
Anyway, that doesn't help you now. Try selecting youyr formulas and going Format>Cells and changing to Text format and now replacing '= with = You will then have to convert the cells back to eg General format and then do a Find/Replace with = for = to convert back to actual formuals. Hopefully this will work - post back if not and we'll try something else.
Hope to help!