Has anyone seen issues with design table …

Has anyone seen issues with design tables in SW2008? I am running into a couple problems here. Sometimes when I close a design table it won’t let me reopen it until I close and reopen SW. It tells me that another instance of the design table is open. The other is the time that it takes to open them in excel. I am having some of these take around 3 mins. to open up. Any ideas?