Site and admin showing plain text only on 1 computer

Hi.
just had a strange problem occur. while editing one of my sites in the admin panel, with the site open in another tab, i removed an image from a gallery, and then refreshed the site. the site then appeared in plain text. i refreshed the site a few times and it would change each time from almost showing the whole site apart from a few images not loading, or full plain text, or part of each or just simply a white screen with nothing loaded at all. also when clicking through the admin panel, im getting the same issues.

its almost like the internet connection is not gathering enough of the page information to display it all correctly as sometime happens on my mobile when the connection is rubbish

Ive done some trouble shooting. I spoke to a friend on the phone who logged in to the admin panel and checked the site and it was viewing fine his end. so it must be my end somewhere. I tried loading it on safari instead of chrome thinking it may be a chrome issue, but it shows the same problems. Luckily i have 2 different internet connections at home. Ive tried it on both and the same problem occurs on both chrome and safari. Now I also have 2 computers luckily. so i tried loading it on the other one and all is fine on both connections and both browsers. so it leads me to believe that somewhere down the line, the problems lie with my imac. Only thing is i have no idea where to start. ive cleared all browser caches and settings, updated OSX and even tried restoring to earlier this morning on time machine but all to no avail.

Anyone have any ideas?

thanks in advance

paul