I think the problem is that you can only resize by moving the end of a partition and not the beginning of one.
so if you shrink your ntfs partition you then can not move the start of the ext3 partition next to it to extend it.
what you could do is create a new ext3 partition in the free space.
move the data from the one partition next to it (could be / partition so dangerous and there may not be enough room).
then delete the partition you copied the data from and extend the new partition over where the old one used to be.
if you post: fdisk -l
this would give us more info.