Interesting.
Looking back in history I see that coolcapricorn.com -was- part of coolhotmail.com, and that coolhotmail.com is still owned by Microsoft :
Registrant:
Microsoft Corporation
Domain Administrator
One Microsoft Way
Redmond, WA 98052
US
Email:
domains@microsoft.com
Registrar Name....: CORPORATE DOMAINS, INC.
Registrar Whois...: whois.corporatedomains.com
Registrar Homepage:
www.cscprotectsbrands.com
Domain Name: coolhotmail.com
Created on..............: Mon, Aug 06, 2007
Expires on..............: Sat, Aug 06, 2011
Record last updated on..: Mon, Aug 03, 2009
Administrative Contact:
Microsoft Corporation
Domain Administrator
One Microsoft Way
Redmond, WA 98052
US
Phone: +1.4258828080
Email:
domains@microsoft.com
Technical Contact:
Microsoft Corporation
MSN Hostmaster
One Microsoft Way
Redmond, WA 98052
US
Phone: +1.4258828080
Email:
msnhst@microsoft.com
DNS Servers:
ns1.msft.net
ns5.msft.net
ns4.msft.net
ns2.msft.net
If it's true that Microsoft let the domain expire, let it stay expired for some time, and now someone else owns it, there probably isn't much you can do about it.
Your timeline of the problem suggests Microsoft dropped the horoscope domains during the recent Hotmail upgrade :
http://www.emailquestions.com/email-articles/2292-new-windows-live-hotmail-features.html
It's a little odd since domains don't expire on demand. The timing is possibly a coincidence.
Try posting a support question in Microsoft's support forum here :
Hotmail Threads
And please let us know the link to your question after it is posted so we can track the issue too.

-Raymond