You could try to use a VPN that prevents your ISP from intercepting the traffic.
You can also limit UL Links to 1 concurrent download and use other values for other hosts at the same time.
Even with one by one download, JDownloader offers enough advantages and is not *useless* in my eyes. Download files in browser one by one. You have to do it yourself vs automated via JDownloader. Just my two cents.
__________________
JD-Dev & Server-Admin
|