Lock request timeout period exceeded error when expand table list in SSMS 2008 R2

Hi All,

I know this question has been asked several times, but nothing fixed my issue. I have been facing the error "Lock request timeout period exceeded. Error 1222 when I try to expand the tables list in a database using SSMS.  SP_WHO2 shows that, a blocking is created by a system process with spid '7', which can't be killed. Tried all possible options that i have got from web. Even server reboot didn't help. Implicit_Transactions, Lock Count are perfect. Please help me. 

Details:

Microsoft SQL Server 2008 R2 (RTM) - 10.50.1617.0 (X64) Enterprise Edition

Windows server 2008 R2 Enterprise

Thanks in advance.