And in case you haven’t seen this elsewhere: Do not install the .NET 3.5 Service Pack 1 on any servers running Sitecore. Service pack updates the LosFormatter class which is responsible for viewstate serialization/deserialization in the ASP.NET, and it looks like they’ve introduced a subtle bug that hit us.

An official release:

Dear Sitecore Enthusiast,

You are receiving this message because you are subscribed to the Sitecore Product Issues and Patches mailing list.

On Monday, August 4th, Microsoft released the following service packs: Visual Studio 2008 SP1 and .NET 3.5 SP1.

Sitecore has discovered that these service packs introduce a bug in the LosFormatter class (System.Web.UI.LosFormatter in System.Web.dll, used to serialize and deserialize an ASP.NET ViewState). This bug causes stability issues in Sitecore products. Sitecore has raised this as an urgent priority issue with Microsoft (case number : SRQ080813600454) and is working to help resolve this issue.

In the meantime, PLEASE DO NOT INSTALL .NET 3.5 SP1 and Visual Studio 2008 SP1 on any server running a Sitecore product (including Sitecore WCMS, Intranet Portal, and Foundry) until further notice!

Symptoms associated with installing either of these service packs:

1. Memory consumption increases dramatically and single core CPU usage goes up to 100% when opening the Access Viewer or Media Library applications.
2. OutOfMemoryExceptions thrown in the Desktop and Content Editor.
3. The browser becomes unresponsive when accessing Sitecore.

Please be aware that Microsoft  may include this Service Pack as part of the monthly ‘Patch Tuesday’.  Please take steps to avoid the automatic installation of these service packs.

Please be aware that the final version of SQL Server 2008 will require .NET 3.5 SP1.

If you have any questions about this issue, please contact Sitecore support.

Best Regards,
Sitecore Support Team.