Aged Domain Deindex what can be reason?

Hi,

This might my 1st thread. I find useful info here all the time, so i am posting a question with hope to get better answer.

I get a aged domain last month, its registered in 1995, and PR6 with 1000's of quality backlinks.

I purchase it in $$$$, and then i start doing all high quality contents on domain.

around 100+ high quality posts done with images, i put premium theme. site get traffic, but today i check domain completely deindex from google.
i did not put any ad, anything.

then i register domain google webmaster tools, and found a msg , google guide line issue.

is it against google TOS to re establish aged domain?

what is best paractice to do with old aged domains? should i redirect to new domain?

i have many other aged domains, those i am in process to build sites, what should i do?

Hope to get answers. thanks guys.