Error signing into CorelDraw

I've got CorelDraw X6 (with latest hotfix) on 2 XP sp3 machines - works perfectly on one, did until a few days ago on the other - then it stopped. No reason that I can see.

I've written to support - NOTHING. Tried contacting ANYONE to help. NADA.

This forum is my last hope... 

When I try to open X6 I get the Sign In promt (I normally never see it, but now it's there). I enter my username/email and password and get Error.Unknown error.

That's it.

I tried disabling certificate checking in control panel --> internet options -> advanced. I deleted all cookies. I also deleted all TEMP files. No change. I'm paid up (I pay monthly for the past 2 years), I CAN log in on my other machine - but not on this one.

Can anyone suggest something I could do? (or just a direct email to a support person at Corel - if some such person exists...)

Thanks in advance,

Paul