We have a weird intermittent problem with saving from Word 2007 to our SharePoint 2007 (MOSS) document libraries that gives a dialog box that never goes away - it is titled "Content Types" and the message "Getting list of available content types..." with a green progress-type bar that keeps scrolling. It happens a lot on our training server (self-contained virtual machine with separate SQL Server) but more worryingly is happening on our live production server (which is in a medium server farm arrangement - web application server, another server for search/indexing and a SQL Server). All servers in the farms are 64 bit.

It is strangely random - the user has to kill Word 2007, then they recover their document and try to save to the same document library and it saves without a problem. 

It happens more on the training server than the live server. The live web application server rarely goes over 20% CPU (usually around 5%) and memory peaks at 2Gb of the available 4Gb (usually at 1.5Gb) so I don't think its a resources issue. 

The document libraries are customised and deployed using Features in a Solution. The only content type in them is the standard Documents content type. 

**Update** We opened this with Microsoft as a support issue and it is a known issue that is targeted to be addressed in a Cumulative Update hotfix package for SharePoint in February 2009.

*Edit* Copied the above response to an answer so this question could be flagged as answered.