I have created a custom module to add a custom column to sales_flat_quote and sales_flat_order. I have been successful in creating the columns in the database. The problem is the module also has a observer for event controller_action_predispatch_checkout_onepage_index, but when the event is triggered i get 500 error message, and no error details is displayed.

/app/code/local/JestaSoft/AddTripId/etc/config.xml 

    <?xml version="1.0"?>
    <config>
        	<modules>
            	<JestaSoft_AddTripId>
                		<version>0.1.0</version>
            	</JestaSoft_AddTripId>
        	</modules>
    	<global>
            	<resources>
                		<jestasoft_addtripid_setup>
                    		<setup>
                        			<module>JestaSoft_AddTripId</module>
                    		</setup>
                    		<connection>
                        			<use>core_setup</use>
                    		</connection>
                		</jestasoft_addtripid_setup>
            	</resources>
        		<fieldsets>
        			<sales_convert_quote>
               			<trip_id>
                    			<to_order>*</to_order>
                			</trip_id>
        			</sales_convert_quote>
    
            		<sales_convert_order>
                			<trip_id>
                    			<to_order>*</to_order>
                			</trip_id>
            		</sales_convert_order>
    		</fieldsets>
    
        		<events>
            		<controller_action_predispatch_checkout_onepage_index>
                			<observers>
                    			<jestasoft_addtripid>
                        				<class>JestaSoft_AddTripId_Model_Observer</class>
                        				<method>addTripId</method>
                    			</jestasoft_addtripid>
                			</observers>
            		</controller_action_predispatch_checkout_onepage_index>
        		</events>
    	</global>
    </config>

/app/code/local/JestaSoft/Model/Observer.php

    <?php
    
    public function addTripId(Varien_Event_Observer $observer) {
        $item = $observer->getQuote();
        $tripId = Mage::getSingleton('checkout/session')->getNTripId();
        $item->setTripId($tripId);
        $item->save();
        return $this;
    }
    ?>