Yii Can't Autload A Model/class

Dear Yiians,

I'm getting a pretty weird behavior from my Yii project. Everything was OK then suddenly the project stopped to autload a specific model: SystemParameters.php

It was working for at the least 15 days.

I use such model to bring the parameters and constants used in the project. The reason it's an table and not under enumerators or CONSTANT is because the user needs to change every month.

The workaround I've found was to add:

require_once APPLICATION_PATH . DS . 'models/SystemParameters.php';

Any clue of what I'm doing wrong?

PS: yes, my config/main.php includes 'import'=>array('application.models.*', and NO, is not a sensitive case.

Thank you for any help,

Doug.