One of our system database became inaccessible due to lack of space on hard drive.
So we detached that database and after making some space I tried to re-attach and .... begins.

Come up with errors like:

The log cannot be rebuilt because the database was not cleanly shut down.

Now, I wanted to attach the database without .ldf file.  

Follow steps explained by Paul S. Randal on SQL server.

http://www.sqlskills.com/blogs/paul/post/checkdb-from-every-angle-emergency-mode-repair-the-very-very-last-resort.aspx#

Remember: You know there's a command that should be able to help you.

You are not the first person to get that error. There exist solutions and peoples who share it.

 Satalaj.