[Help-glpk] Assertion Failed x>=lb

[claudio . cava]

Hi. I'm Claudio. I've a problem with MIP solver of glpk.
It solves lp relaxion with simplex without problem. But when I use MIP solver
it tells me:
Assertion Failed x>=lb ; glpmip2.c line 218.
What could be? I'm sure upper and lower bounds are all right. I can't sent
you the code because it's too long.
Thanks in advance and congratulation for excelent work.
Claudio