Try this. Type in the address bar about:config. Accept the warning. In the page that appears, in the Filter box, type network.http.max-connections . Change the value to 32 (which is probably set to 256 in your case). Close that page. Restart the browser.

Thanks amkeew, appreciate your fast response and suggestion - setting was as you said so I have changed it. Will need to do some browsing through the day and will report back, but right now all looking good.

Glad it worked. Just mark the post solved so that it moves from unsolved category.