I don't know what to tell you, as no one else seems to have a problem with this filehost, outside of the normal limits for those without premium accounts.
I'll repeat my previous suggestions: Clean out your cookies and cache (maybe your history, too) from your browser(s), try a different browser, make sure some other app isn't blocking you from downloading (Little Snitch, Lion/ML Gatekeeper settings, any AV/Firewall app you may have installed, etc), try adding the links to jDownloader and see if you can download that way. Edit:
If you are using cookie blocking software (such as Cookie, Cookie Stumbler, etc.), this also may be why you're having issues. Try disabling your various apps, boot your browser into Safe Mode (it will disable all extensions and reset your settings to default) and see if you're still having a problem. If not, then the issue is definitely with your settings, one of your extensions or one of your standalone apps.
Restart your browser normally and manually disable all extensions that block cookies, websites, etc, then start adding them back, one at a time. After you add one, try downloading from an uploaded link. Continue until you find the culprit and see if it allows you to change your preferences. Re-enable your standalone apps and do the same.
One thing to check in Little Snitch is to see if you inadvertently created a rule under Any Process (or your specific browser) to block all connections via port 80 (http) and/or port 443 (https). Delete those rules or you will continue to have problems. ONLY block those ports for specific apps, if needed.
Only a few people are having problems, and I've exhausted my memory of what issues could possibly be causing the problem.