Update Rollup 1 for Microsoft Dynamics CRM 4.0 is now available for download on Microsoft’s website at:

http://www.microsoft.com/downloads/details.aspx?FamilyId=57C6267B-3B13-49DD-BFED-3CC83633AEA7&displaylang=en

It’s a software update that contains a quite a few individual updates and hotfixes that resolve issues with Microsoft Dynamics CRM. Here’s more detail on what Update Rollup 1 includes:

http://support.microsoft.com/Kb/952858

This update can be uninstalled but it’s a good idea that you first do a full backup and also consider deploying it to your test environment before installing it in your production environment.