firstly, let me say how impressed i am with your timely response, much appreciated..
My machine is new high powered desktop with 8G ram
windows 7 ultimate
mozilla version 28
java upto date and working
I have checked all your links above and can admit that i had to update mozilla from version 27 to version 28, done.. java is working, adobe is upto date, etc etc..
I installed a premium theme yesterday and was happily customizing the theme without glitch but after about 2 hours of tweaking i noticed strange glitches, such as.. while filling in my personal profile i scrolled back to the top of the page and all my previous data disapeared, this has happened 2 times at which point i went to bed swearing..lol
Today, i can't get any joy at all so i cancelled my premium upgrade as the wp admin was still displaying a go premiumm button at the top of the page and I wasn't particularly impressed with the wsiwg available options... I was hoping it would be easier to fully customise without knowing css etc..
so.. i am about to give up on wordpress and build a joomla site instead.. so, frustrated after completing your above checklist expecting it to work but not.. :-/
maybe there is a config file on my computer which has erroneous settings ? I just cant work out why everything worked yesterday but today nada..