You should be able to do this with the Win32_NTLogEvent Class.

The script below lists all "error" events. You could make your query more specific (and include timestamps, etc)
code:
$obj = GetObject("Winmgmts:").ExecQuery("Select * From Win32_NTLogEvent Where Type = 'error'")

For each $event in $obj
$event.EventCode 
" "
$event.Message
?
Next
For more information on this class, see:

http://msdn.microsoft.com/library/en-us/wmisdk/r_32os4_48ac.asp

Brian