Did you remove the separater bar that is right before the tabs? That has a clear:both on it's div that should have stopped the purchase box from floating up. If so, you need a clear:both somewhere after the VMflyOtherImagesBox images box to stop other things from floating up.
Did you expand the width in the VMflyOtherImagesBox to accomodate the width of two thumbs with any margin or padding?
I have the demo site set up right now to have two columns of thumbs and it seems to work fine on FF and IE. Look here:
flytabs.seemyseat.com/index.php/FlyTabs-Demo/Joomla-Add-ons/Google-Mapping-for-SOBI2-Search-Results/flypage.tpl.html
I can't leave it that way for long so check it out soon.
The changes I made were to remove the clear and change the float to left on .VMflyThumb as we discussed earlier. I also changed the float on #VMflyOtherImagesBox to left and increased the width.
Regards,
Jerry