Have you changed your router at all?
Is all your port forwarding setting still there?
If not here is a free guide on port forwarding for your CCTV:
http://qrcctv.co.uk/cctv/cctv-port-forwarding
Also you are right. It may be the active X. Clean your browsers cache and temp files. (Even try re-installing your I.E again!)
Hope this helps.