Nothing would give me greater pleasure than to tell you about a new! improved! Mussel Bar, a changed restaurant from the listless seafood joint I encountered four years ago in Bethesda. Its owner and creator, after all, is Robert Wiedmaier, the talent behind Marcel’s, Washington’s top splurge for French cooking. Sadly, some of the same problems that plagued the upstart, which is modeled on the Belgian roadhouses of the chef’s youth and now has branches in Arlington and Atlantic City, have stayed on like lingering houseguests who were never welcome in the first place. Oysters on the half shell will not be confused for those cracked open at the trusty Old Ebbitt Grill downtown; Mussel Bar’s thin-crusted pizzas are bested by Papa John’s (and a topping of not so “spicy lamb” is a ringer for meat from a taco kit). Mussel Bar’s roster has been expanded to include main courses of grilled salmon on creamy polenta and specials highlighting herbed rabbit with totems of potato and carrot. Nice ideas, poorly executed. The fish smells like last week’s catch, and the rabbit is framed with vegetables so undercooked they almost crunch. Three cheers for the many good beers, though, and the steamed mussels (now Blue Bays from Prince Edward Island). Does our eager server really believe every dish is as “great” as she says? Whatever, she knows her way around the suds and, better yet, keeps ’em coming.