Failed to get list of publishing queue items. Timed out

I'm on Tridion 2009 SP1. At some point, the ability to view the publication queue for all users (i.e. Not Filters) simply stopped working. The CM GUI accepts a timeout error:

(80040E31) Timeout expired
Unable to get list of publishing queue items.

SQLUtilities.OpenRecordsetByStoredProcedure
SystemDAL.GetListData
SystemBLST.lObjListPublishTransactions
SystemBLST.IBLSystemST_GetListData
ManagementInfo.GetListPublishQueue
Request.GetList

So I tried using the Powertool Publishing Queue Manager to clear the queue, but that just throws a 500 error, which is consistent with having too many items in the queue.

Then I tried to clear the queue using the Tridion Purge Tool, but it crunches for a few seconds and returns the same error:

14-May-2012 21:10:12 Log cleared.
14-May-2012 21:10:12 Purge action started at 14-May-2012 21:10:12
14-May-2012 21:10:12 Keeping the last 5 versions.
14-May-2012 21:10:12 Recursive mode: False
14-May-2012 21:11:12 FAILED: <?xml version="1.0"?>
<tcm:Error xmlns:tcm="http://www.tridion.com/ContentManager/5.0" ErrorCode="80040E31" Category="7" Source="Kernel" Severity="1">
    <tcm:Line ErrorCode="80040E31" Cause="false" MessageID="4613"><![CDATA[Unable to get list of publishing queue items.]]>
        <tcm:Token>RESID_4485</tcm:Token>
        <tcm:Token>RESID_15821</tcm:Token>
    </tcm:Line>
    <tcm:Line ErrorCode="80040E31" Cause="true">
        <![CDATA[Timeout expired]]>
    </tcm:Line>
    <tcm:Details>
        <tcm:CallStack>
            <tcm:Location>SQLUtilities.OpenRecordsetByStoredProcedure</tcm:Location>
            <tcm:Location>SystemDAL.GetListData</tcm:Location>               
            <tcm:Location>SystemBLST.lObjListPublishTransactions</tcm:Location>
            <tcm:Location>SystemBLST.IBLSystemST_GetListData</tcm:Location>
            <tcm:Location>ManagementInfo.GetListPublishQueue</tcm:Location>
        </tcm:CallStack>
     </tcm:Details>
</tcm:Error>

All event logs display the same error. Oh, and yes, I tried to restart the COM +, Publisher, and Transport services.

, , . , ?