Hi Alec,
Thanks for the link. I have applied the patch, although it does not solve the issue.
I think my issue is different from that of the patch.
The parent folders that cannot be re-subscribed are not actually the special folders (inbox, drafts etc) but user defined folders which would sit alongside the special folders. For example, if you had the following folder setup
Inbox
Drafts
Sent
Junk
Deleted Items
Folder 1
__Folder 2
____Folder 3
__Folder 4
Folder 5
It would be Folder 1 and folder 2 that have the unsubscribe/subscribe issue (parent folders), whereas Folder 3, Folder 4 and Folder 5 (don't contain child folders) would unsubscribe/subscribe as expected.
Any further thoughts would be appreciated!