ActionScript 2.0 :: Array Overwriting - Reference/value?

I've created two custom classes to contain data for a web forum controller flash tool:

class postClass
{
public var post_id:Number;
//plus some other variables like timestamp etc

[code]....

When I try to assign a new post to a user (by adding the post data to the postArray variable) I overwrite posts that I had already placed under other users. More specifically, if I'm posting the first post for User Y, I overwrite the first post for User X with the exact same data.I thought this was a reference vs. value passing error, but I tried to eliminate this by not copying the "postClass" objects, but assigning the data directly into the user's postArray array:

var userArray:Array = new Array();
function addNewUser(masterPostIndex,UserNumber)
{

[code]....

This all seems to work fine until I try to write a new post for a second or third user. If I trace the contents of User X's posts, they immediately become identical to the content of User Y's posts, as soon as User Y's posts are added. Later, when User Z comes along, both User X and User Y's posts are overwritten. This code is kinda long, so I didn't want to post the whole thing - but I can post any parts you're interested in, of course.

This really 'feels' like a reference-passing error (arrays are all looking at the same location in memory), but I can't figure out what I'm doing wrong - I'm not making a postClass object and then pushing it onto the user's postArray (I tried that too, same result).

var newPost:postClass = new postClass();
//read and assign values to newPost
userArray[userIndex].push(newPost); //

this is clearly passing the referenceI can see how the latter example would pass the reference to newPost to the user object, then when I change newPost in the next iteration (when user Y posts something), User X's data will change too. I tried to avoid this with the first set of code.