Hi,
I still don't see the problem. Here's a smaller example.
A = RandomReal[{-1, 1}, {5, 5}]; B = RandomReal[{-1, 1}, {5, 5}];
sols = Solve[Det[A - w^2*B] == 0, w]
This gives:
{{w -> -0.890446 - 0.570123 I}, {w -> -0.890446 + 0.570123 I}, {w -> -0.604951}, {w -> 0. - 1.01964 I},
{w -> 0. + 1.01964 I}, {w -> 0. - 1.82466 I}, {w -> 0. + 1.82466 I}, {w -> 0.604951},
{w -> 0.890446 - 0.570123 I}, {w -> 0.890446 + 0.570123 I}}
If you now apply the command I posted earlier:
Select[Chop[w /. sols], (Head[#] == Real && Re[#] > 0) &]
It gives
{0.604951}
which is indeed the only positive real solution that Mathematica found. So what makes you say that this does not work?
Cheers,
Marco