Hi Roshni,
I've checked two of your sites if they were banned, and records indicate the following: "The domain name has no records with Google. It is either new or MAY BE banned." Your sites are pretty old, 2004 and 2005, they are not new, so very possibly they were banned.
I also checked one of your site "
www.luxurycarhireindia.com" and I noticed it has too long "title", "description" and "keywords" meta tags. "Title" contains 134 characters instead of 80 recommended, "description" contains 353 characters instead of 250, "keywords" contains 525 characters instead of 500, and the most important their relevancy is poor. Google likes Friendly Environment!
I also noticed that your "title", "description" and keywords" looks like they are stuffed with keywords (Google likes friendly and natural description)
Also your page contains 120 urls. Some Search Engines have problems with more than 100 urls on a page.
I'm not sure about if my other guess is correct, but if you recently changed your hosting or IP address, it might also affect your Google temperarely drop (once again I'm not sure if this is correct statement).
It's hard to say what exectly might course your problem, but what I listed above might take affect.
If I have a chance to look at your other site, I will do that later.
Hope it helps.
Have a great day,
Peter