Unfortunately this is how is has been with Mono since 2004, each release has bugs and new releases fix some and new ones are introduced. It is always a hit or miss, your mileage may vary kind of thing running complex web applications like mojoPortal on Mono. That is why I do not recommend for anyone to use Mono for any important production sites running mojoPortal. I had hoped that eventually it would become a stable platform for web apps but it never quite gets there. The Mono team are always chasing a moving target because .NET and ASP.NET keep evolving. Every now and then a Mono release seems pretty good with only a few minor bugs but never have I ever had it run mojoPortal with zero bugs.
Best,
Joe