I think you have misunderstood what I was talking about - I should probably have made it clearer, sorry.
I realise that the page file is in use while running windows and so can't be defragmented - the only reason I mentioned it was to explain why I was also using diskeeper (since it is one of the few apps available that can defragment the page file in Windows 7 x64).
The bug is not related to the page file, but to other files not currently in use.
How the bug occurred:
Closed all open programs and stopped all services able to be stopped (via services.msc)
Defragmented all drives with defraggler till it told me no files were fragmented (excluding non-defragmentable files; page file, $MFT, etc)
Opened diskeeper and analysed all drives
Noticed that diskeeper said several files were fragmented
Defragmented all drives with diskeeper (which defragmented several files)
Analysed all drives with both defraggler and diskeeper
Both now say no fragmented files (again excluding non-defragmentable files; page file, $MFT, etc)
Note that on some drives defraggler listed no fragmented files at all (including non-defragmentable files), yet diskeeper told me there was files that were fragmented on the drive (which is was able to defragment).
The bug, then, is simply that diskeeper apparently found and was able to defragment file that defraggler did not.
I hope that makes more sense!