I use Firefox and was looking at a site earlier and turned off javascript to see what all the noscripts were doing. Turned it back on afterwards. I've since closed down firefox a couple of times and if I visit other sites the JS is working fine (including vB 3.5 forums). However on DP it thinks the JS is still turned off! Something flaky in there?
Try turning on the Javascripts again and make sure DP is not in exceptions list, this is how you can do it: In the Firefox menu bar, click on Tools. In the drop-down menu that appears, click on Options. The Options window will appear. In the left column of the window, click on Web Features. On the right side of the window, make sure Enable JavaScript is checked, then click on the OK button. Check if DP is not in 'Exceptions' list.
There is nothing special as far as JavaScript detection goes going on within this forum (no cookies or anything else). So to be honest, I don't have the slightest idea why that would be happening.
Nothing changed on this end either. I think it's 100% based on user agent (when vBulletin tries to use JavaScript stuff), so maybe your user agent was being altered/wiped out somewhere along the way.