Asynchronous?

I havn't worked much with Asynchronous callbacks so I'm here for some help from the throbing brain...

I have a program that scans all computers on the network and checks for a specific file, returns details about that file. I have a listview and on the callback I'm populating the results that the asyc function returns. But occasionally some of the results in the listview turn up blank. I'm not sure why... I'm running my async calls in a for loop... like this

Dim cb As New AsyncCallback(AddressOf Me.ResultsCB)
For x = 0 To aryComputers.GetUpperBound(0)
Dim ar As IAsyncResult = cd.BeginInvoke(aryComputers(x), _FilePathName.Text, cb, Nothing)
Next

are my callbacks coming in at the same time and overtaking my results function to update my listview?

Any help is appreciated..., or even a "you're stupid" comment is always nice too....

Where is the code for the callback? Are you using Synclock to make sure multiple threads don't try to access anything at the same time?