Desperate! "Unable to login at this time";how to access a "no entry" folder

Question

I started my Mac this morning but everytime I try to login in my account it says "You are unable to log in to the user account at this time".
I have tried running disk utility. Nothing changed.
Since I have FileVault activated I tried to repair my Rick.sparseimage file using these instructions:
http://docs.info.apple.com/article.html?artnum=25695
...but I can't access my Rick folder, it has a "no entry" sign and doesn't allow me to access the contents.
Questions:
1- Is there any way of turning off FileVault using Terminal?
2- Is there any way I can access a file that has the "no entry" sign over it?
3- Any other solutions to my problem? I'm desperate!

Answer 1

I noticed by using searching the forums that I am not alone in my problem and many of you have lost valuable data trying to figure out how to regain access to your accounts.
I am not at home so I can't test the suggestions I've found all over the web. Here is one that I will test later:
A fix for a FileVault home directory repair issue
http://www.macosxhints.com/article.php?story=20060115133107555&query=filevault
I've also seen this in another thread:
To at least try to distinguish between these possiblities, try logging in to the other "admin" account, and begin by changing the password of the affected account back to what it was originally. Then try opening "/Applications" > "Utilities" > "Terminal.app" and entering these commands (in all lines, where it says 'username', substitute the affected user's short name, and enter the affected user's password when prompted):
su -l username
ls -ald /Users/{\.,}username
find /Users -name username.sparseimage -print -exec hdiutil attach {} \; 2>&1 |grep -v ^find
The output and results of the above commands might provide an indication of whether or not the problem is fixable...