Fatal error: Smarty error: [in evaluated template line 15]: syntax error: unexpected

Ok, got an issue. Just started a real-estate classified website and configured so it would fit my tastes. Since yesterday, the users that want to add an ad can go all the process up to the last step, where, instead of the page with the message "Ad post successful!" are getting this error:

Fatal error: Smarty error: [in evaluated template line 15]: syntax error: unexpected {elseif} (Smarty_Compiler.class.php, line 495) in /home/geloo/public_html/imob/libs/Smarty.class.php on line 1092

also getting this if i want to go back from the page above:

Parse error: syntax error, unexpected '{' in /home/geloo/public_html/imob/libs/Smarty.class.php on line 1075

What would cause this kind of error, how can i discover the problem?
I really need help, since I am newb in PHP, started some weeks ago to learn.

I figured out that could be an error caused by something in the database, since when I tried with another clean database, it worked just as it should.

If you want to see the process where the error appears, use this link:
http://imobilis.info/newad.php - username: help - password: help. The error occurs at the last step, wich is /newad.php&step=7 or /free_return.php.

If there is some info more needed, please tell me. Thanks in advance.

The first is a custom application error; for that you'll need someone that knows smarty templating.

The second is a syntactical error in the code for Smarty.class.php. That indicates code was modified within that class causing it to no longer function as it throws an error during compilation. Given its name I'd suspect that its important for the system itself, so you'll need to figure out what has changed and either fix it or revert it.