With Free Pascal 2.4.x and 2.5.1 on Windows, you must disable floating point exceptions as soon as possible in your program. Add the Math unit to your uses clause and add the following statement at the beginning of your program:
       SetExceptionMask([exInvalidOp, exDenormalized, exZeroDivide, exOverflow, exUnderflow, exPrecision]);
http://wiki.lazarus.freepascal.org/GeckoPort