The problem is probably due to either DNS lookup problems, or a trap storm. How many messages are you attempting to load into the browser? Also run an C:\>ovstatus -v netmon and see how far behind the netmon queue is for DNS lookups, and what the longest lookup time is.
If you are getting a trap storm (1000s of messaged attempting to load) find the source of the storm and stop the devices from sending the traps or add an access list to your border router to deny port 163 from the offending devices until you can fix them.
If the delay is from long DNS lookups, solve your DNS problem. This could be due to many factors. Post again when you get the info.