Performance Slowness when a new window has to pop-up

 Agile 9.3

Hi, We are experiencing a huge delay in launching a pop-up window or user pallett  whenever a new window has to pop-up as a result of our actions in PLM. This performance slowness is random and doesn't occur at the same time of the day or with the number of users logged in. The users who all complained about this issue are all using IE or FireFox. Are there any specific issues logged for these web browsers? Can anyone shed any light on this or any workaround for this will be greatly appreciated. Our diskspace, memory etc have enough space while