Vista - Mozilla Lightning 0.9 and Vista 64bit

Does anyone have experience with Vista 64 and Mozilla Lightning? I've run into an issue with Lightning 0.9 not allowing me to edit accepted invitations (such as setting a category for the event). My problem is I switched to Vista 64 bit at the same time I upgraded Lightning from 0.8 to 0.9, so I don't know which is causing the issue and the Mozilla forums are bereft of answers for this problem.

Now when I accept an event invitation from someone else, the window below is the displayed window rather than the standard task window where you can set event details. You can right click on the event and select "convert to task", which will bring up the standard task window, however any changes made are not saved and the event simply reverts back to the window you see here.

I've searched around to try to find a way to revert to Lightning 0.8 to try that, but the file has been pulled from all Mozilla servers, so that option is out. I'm hoping maybe somebody else has ran into this and knows a work around if it's a Vista 64 incompatibility issue.