Our 2008 r2 file server has intermittent drops. it will have brief periods where no one can browse the files so they can't download or upload to/from the server, so it's causing a lot of problems for some of the heavy users. It's not losing any pings, can ping constantly without any drops. Other servers on the same node don't have this problem, or else it's not noticeable because they're not as heavily used. What can cause it to drop intermittently like this?