Get-WinEvent - Security

I've been trying to use eventcombmt to find some user logon attempts but the application crashes. Since there are no other alternatives I thought PowerShell would be my friend.

I need to crawl the Security log which appears to be working but its showing blank Messages.

Get-WinEvent -Path .\Security_A.evtx -Oldest | Where-Object {$_.ID -eq "529"}


   ProviderName: Security

TimeCreated                     Id LevelDisplayName Message
-----------                     -- ---------------- -------
18/05/2013 00:06:38            529
18/05/2013 00:06:38            529
18/05/2013 00:16:38            529
18/05/2013 00:56:38            529
18/05/2013 00:56:38            529
18/05/2013 00:56:38            529
18/05/2013 01:06:38            529

Any ideas?

One thing I guess I should mention is these are from a Windows 2003 DC converted from EVT to EVTX. They open fine in Event Viewer.

PowerShell is running with Administrative privileges.