Google can't fetch my website!! please help

Noticed that there is a big drop in my website's (a SMF2 Forum) stats, so just headed to my google webmaster panel. I was trying to submit a sitemap, but this was Google's response:

I changed the robots.txt file, uploaded it to the same folder

but the same error was shown
this time I just simply deleted robots.txt file

and got 1 error+ 1 warning:
error:

I googled robots.txt + some other related words, and found that when google is saying that robots is out of reach, this could also mean that google cannot see your website at all. accordingly, I used the fetching tool of google,
here comes the strange problem:

google was not able to fetch my forum in its wellknown address (example): http://forums.MY WEBSITE.com
but it was able to fetch http://www.MY WEBSITE.com and http://www.MY WEBSITE.com/forums

how can I fix this?


BTW,
I have another forum on my host, the same SMF2 forum, and it was ok, google was able to fetch it

first of all I must mention that I have searched the forum for find the answer but seems this problem is a quite new one

 

Try to Check you robots.txt file permission from hosting account. May be this file permission using no access permission.

Best of luck

 

I have already deleted it to make the problem a bit simpler

 

I would like to suggest you one thing on this point is, why dont you try delete entire ftp folders and Db. and re upload and install Forum. Then go with robot.txt file. It should start working...
(pls take backup before do this) (of-course )

 

Thanks for your suggestions

yeah I almost did that
For those who may have the same problem, it really seemed a very killing job to solve, so I just created a new subdomain and redirected that old subdomain using 301 redirect, and sure in permanent