disconnection

This isnt good at all. I have being have frequent disconnects no interms of the interface connected to the network but in terms of messengers diconnecting for a long time and even web page becoming unneccsarily slow and atimes show cannot find server while all you have to do is refresh them and they work again. please help. i have alot of firewall rules if that could be a problem. i also have alot of macs in the access list and yeah i use a rb500 series