well you can isolate the situation, is this space always above top members or always below recent posts? [no matter what hook is above(top members) or below(recent posts)] once this is determine check out the styles css for the specific hook and search around for an extra pagebrake or spacer (<br><b/r> <p> ) or something along those lines , maybe even a floating script, towards the affected area of whichever hook it seems to be
recent posts -obvi towards the bottom.
hope i helped.