OK, I've patched lyxpreview2bitmap.py, take a look at the attached file and tell me if it works for you. I've attached also some test LaTeX files I've tested. It seems we've reached a very good solution, I'm really satisfied. Now we need some testing.
venom00
detect_specials.diff
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xypic.tex
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maths.tex
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pstricks2.tex
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