QTP tests are not running from QC - Failed (!)

This is a rushed post as I collate my thoughts around why my tests are not running 2 1/2 days before a release.

So I've recently set the remote agent to restart after 10 runs, in hope of reducing the likelihood of QTP crashing mid-run. 

My problem: suddenly every tenth test I run from QC crashes.

Hmm. 

Change remote agent restart value to 1

Now every test fails. 

Logs

With medium level logging I see: 

"Error...CRemoteAgent:get_value Pier is NULL", and

"Error...SetDisplayKeywordView : Automation is null"

I tried restarting the machine

Firstly, I've tried updating Remote Agent settings (all values aside from the restart testing tool after x). Problem persists.

I've given up and set QTP to restart after every 0 tests. My tests are now running. I will have to carry on investigating when I am not 2.5 days out from a major release. If you've seen this / know how to fix please post a reply.

Notes on my environment

Windows XP

QC ALM 11 (mid-tier license, from memory)

QTP 11.00.0.0 Build 1018