My software update server is clearing its config file

I have installed Lion Server and the Server Admin tool. I have configured Software Update Server and it spent a night downloading all the udpdates, and was working for a while, so far so good.

Then it suddenly stoped working the next day. Any attempt for a client to run software udpate results in a dialogue box declaring "Software Update Server (imac.local) is not responding"

The sevice is enabled and its dot is green in the list.

The following message appears constantly on the console:

25/08/11 9:52:53.282 PM com.apple.launchd: (com.apple.swupdate.host[31312]) Exited with code: 1

25/08/11 9:52:53.282 PM com.apple.launchd: (com.apple.swupdate.host) Throttling respawn: Will start in 10 seconds

Occasionally this group of messages appears:

25/08/11 9:51:46.341 PM com.apple.SecurityServer: Failed to authorize right 'system.install.app-store-software' by client '/System/Library/PrivateFrameworks/PackageKit.framework/Versions/A/Resources/in stalld' [31265] for authorization created by '/System/Library/CoreServices/Software Update.app' [31259]

25/08/11 9:51:46.341 PM com.apple.SecurityServer: Failed to authorize right 'system.install.software' by client '/System/Library/PrivateFrameworks/PackageKit.framework/Versions/A/Resources/in stalld' [31265] for authorization created by '/System/Library/CoreServices/Software Update.app' [31259]

25/08/11 9:51:46.421 PM Software Update: SoftwareUpdate Scan: Error Domain=NSURLErrorDomain Code=-1004 "Could not connect to the server." UserInfo=0x7ff7c5c01f80 {NSUnderlyingError=0x7ff7c5827410 "Could not connect to the server.", NSErrorFailingURLStringKey=http://imac.local:8088/index.sucatalog, NSErrorFailingURLKey=http://imac.local:8088/index.sucatalog, SUCatalogFetchOverrideURLString=http://imac.local:8088/index.sucatalog, NSLocalizedDescription=Could not connect to the server.}

In the admin tools, the error log for the SUS is reporting:

Syntax error on line 241 of /etc/swupd/swupd.conf:

Port must be specified

However the port 8088 is listed on the config pane etc. But sometimes when I stop and re-start SUS this port is cleared. Just FYI, my other settings are no limit to bandwidth, udpates stored in the default /var/db/swupd/ and all other check boxes off.

Looking at the config file in /etc/swupd/, line 241 reads:

Listen *:portToUse

Any attempt to change this is overwritten next time the service starts. The owner of the config file is root, however the user _softwareupdate owns all other files in the directory save the file swupd.conf.previous, .start_time, and swupd.plist which are all owned by root (-rw-r--r--)

I did attempt to change the owner to _softwareudpate for these files, however this was changed back on the next restart of the service. I have also tried to run permissions repair in disk utility which did change one file in this directory.

I worry that if I trash the server and start again this problem will re-appear and I also don't want to loose the 9Gb of updates I have already downloaded.

Is someone able to help?

Many thanks in advance for any assistance.