Can’t Drag and Drop Widgets

First up, I know this has been mentioned before but I cannot find a solution that works for me.

I cannot drag and drop widgets on my Sidebar. It wokred fine for a while but now the only way is to deactivate all plug-ins and then drag the new widget and then re-activate the plug-ins. This is OK but a pain as the more plug-ins I use, the longer is takes to re-activate.

I’m using version 2.3 of WP.