Todd Carter has found a core issue with SharePoint 2007 relating to the way that memory is disposed. Over the past couple of years memory management has become quite a hot topic and best practises have been published such as ensuring that you dispose of certain SharePoint objects (e.g. SPSite and SPWeb) after using them. These discoveries have lead to tools such SPDisposeCheck being released.
Todd however thought there was more to it and has investigated into SharePoint’s memory usage even further and uncovered a bigger issue.
An interesting article delving into the internals of Sharepoint, explaining the problem and then providing a workaround, a full fix is due shortly.
Funnily enough SharePoint 2010 does not seem to suffer from this problem, maybe thats a good reason for a client to upgrade!