SQL Server will take all the memory on a system that you let it take and it will hold on to that memory pretty much indefinitely. It's not a problem. It's by design. But, you should put a limit on the max memory.
However, if you think you might be under memory pressure, I have an article [/url]that shows two quick ways to determine if that's true. The query for reading the ring buffers was problematic for some people, but there was a suggested fix in the comments. Just scroll down.