Could you post the full error message?

There's a connect item related to restoring a SQL 2008 database using SSMS 2012 GUI, which posts an erroneous error message about LSN chain breaks, are you hitting that scenario?

http://connect.microsoft.com/SQLServer/feedback/details/755813/sql-server-management-studio-2012-errors-when-doing-restore-to-sql-2008

It should still work through T-SQL restore commands if you're hitting that