Unable to resize partition bigger, after shrinking it

Hi there

I tried to resize my Boot Camp partition, following the advice here:

http://kb.parallels.com/en/112984

I was able to reduce the size of my main Macintosh HD partition [Mac OS Extended (Journaled)] -- but then unable to increase the Boot Camp one in Windows (Extend Volume... was unavailable -- something the Parallels knowledge base overlooks). In the end I purchased and used Paragon Camptune X to achieve this succesfully.

However, this software did not take advantage of the 'unallocated' space that I created in the first step of the Parallels approach, so I have been trying to use Disk Utility to resize the partition to fill the gap. However, while it lets you drag down the partition and click Apply, this eventually fails with the error "Partition failed for disk ST9500325ASG Media Couldn’t unmount disk." I have tried several times, both from the recovery HD and directly, but I cannot seem to expand the Macintosh HD partition up by the amount I reduced it earlier.

I usually get the unable to unmount disk error, but on some occassions it looks like it has done it, and I get logs like:

Beginning partition operations

Unmounting disk

Finishing partition modifications

Waiting for the disks to reappear

Partition complete.

But it does this very quickly, and it turns out that the size has not been adjusted.

Any ideas on how I can relcaim the unallocated space?!

Many thanks in advance.