The most likely scenario is that you have an underlying javascript conflict on the site which the uploader plugin scripts has encountered. This is more likely to be the case if there are other functions that also do not work – like reply to a topic for example – but if generally, the page loads correctly.

Do you know how to use the console within your browser to check for errors? If not – you can let us have a link to your forum page so we can take a look if it is public.

The site is still under delevelopment and i’m develpoing offline. Yeah the reply  function is not working too. I disabled all other WP plugins and left only SP with the file uploader plugin enabled but i’m still getting the error. I’ll investigate further

Might be worth switching to a default WP theme briefly to see if something in the theme is causing the problem. 

I’m currently on the 2012 wp theme. I’ll try other default WP themes

if you have stripped all WP plugins and potentially non-standard themes out of the equation then such a conflict seems less likely. Although checking with the script console would still be advisable.

The only other thing that comes to mind might be some sort of corruption in the upload plugin code made during download. Very unusual and rare but it has been known to happen.

I have figured out the source of the problem. I have an ad server nn my lab (Revive Ad Server) and i have some ad tags on the header and footer temaplate files of the SP theme i’m using. I removed the ad tags and everything is working. I’ll take from here

Excellent, thanks for letting us know.

Hopefully should be fairly easy to correct as well.