Unable to create Table in SSMS 2005

Hi all,

i have a problem when i try to create DB or new Table or Open table definition i got this error message

Unable to cast object of type 'Microsoft.SqlServer.Management.Smo.Urn' to type 'Microsoft.SqlServer.Management.Smo.Urn'. (SQLEditors)

How can i solve this problem

Information about SSMS like below

Microsoft SQL Server Management Studio9.00.3042.00
Microsoft Analysis Services Client Tools2005.090.3042.00
Microsoft Data Access Components (MDAC)6.1.7600.16385 (win7_rtm.090713-1255)
Microsoft MSXML3.0 5.0 6.0 
Microsoft Internet Explorer8.0.7600.16385
Microsoft .NET Framework2.0.50727.4927
Operating System6.1.7600

Thanks