I originally wrote the TortoriseHg review board user interface to use a fork of Mdelagra’s fork of the original mercurial extension.
I have since made some changes to the UI I wrote earlier this year (goo.gl/AHKJE) to make use of a fork of the original extension instead.
I did this because the original extension that is listed on the Mercural website (goo.gl/nWMdS) has recently been update to support the Review Board API 2.0 that was shipped with Review Board 1.5. This updated API has some nicer features that I have implemented, namely, the more granular control over filtering review requests.
So I have forked the original and, among a couple of bug fixes, added some features to make it play nicer with the TortoiseHg review board dialog. This fork is now required to be used with TortoiseHg and can be downloaded here – goo.gl/cTdci
I have made contact with the developers of the original extension and hope to get my changes merged into it some time in the new year.
Hopefully before the release of TortoiseHg 2.0, however in the mean time my fork will have to suffice.