With our help (in the frame of our work on Mantis in the Helios project), the version in Debian testing of Mantis is now in sync with upstream (1.1.8) : http://packages.qa.debian.org/m/mantis/news/20090709T163923Z.html
Next steps, integrate Mantis in the Helios platform for real… and maybe more contributions in Mantis, and maybe on the Mandriva packaging of it. Stay tuned.