There are quite a number of things that could be at fault here, especially given the clustering setup you have. I would review every error log you can get your hands on before going to external support. I believe you can get better and MUCH less expensive help than Microsoft CSS too, but I am a tad biased on that statement. :hehe:
Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service