I just read this: http://www.lavasoftsupport.com/index.php?showtopic=8253

How odd that a definition file update ends up requiring un-installing and re-installing the subject software.

Anyone able to explain this?

This is a known issue - The problems with ISP/Error Retrieving Update issues has now been fixed.

Please see the pinned post by LS Digger Barnes here:
http://www.lavasoftsupport.com/index.php?showtopic=8253

The current discussion if you wish to post additional information or problems is here:
Auto Update Server Down?
{Topics Merged} Updates Problems go here
http://www.lavasoftsupport.com/index.php?showtopic=8059

In some cases, it may not be possible to update via Webupdate, we recommend that you try performing a manual update. To do this:

Manual Update*
In some circumstances, you may not be able to update the definition file by using WebUpdate. Reasons can include the server being too busy to process update requests, or proxy settings are not configured correctly in Ad-Aware. You can download the reference file manually using the following steps.

1. Close Ad-Aware

2. Download the latest definition file in a ZIP file from Lavasoft's website*
http://dlserver.download.lavasoft.com/public/defs.zip
3. Save it to a temporary location

4. When complete, unzip the contents of the file, either through your favorite ZIP utility or through built-in support in Windows, to the installation directory of Ad-Aware, which is usually C:\Program Files\Lavasoft\Ad-Aware SE\

5. Open Ad-Aware

You can then confirm the latest definition file is installed by looking at the Initialization Status on the main Status screen.

I'll go ahead and lock this thread so that we don't have multiple topics going on the same issue