I updated Silverlight on my Mac from 4.x to 5.0 today. The main reason was the have what was presumably the best experience for Netflix which requires Silverlight even on a Mac. Unfortunately, it looks like Silverlight 5 breaks Google Chrome. After the update, Chrome spawns zombie processes. The result is that Chrome becomes unusable after starting up something that uses Silverlight like Netflix. The only way I could shut Chrome down was to open a terminal window and use kill to terminate Chrome.
To make matters worse. The Microsoft Silverlight downloads page with a link to Silverlight 4 actually leads to a version 5 download. The end result is I cannot visit any webpage that uses Silverlight without breaking Chrome.
UPDATE: Silverlight 5 does not seem to have problems when used with Firefox under OS X.
Microsoft Silverlight 5 for Mac OS X (Snow Leopard in my case) continues to be a problem for me (earlier reference here). The screenshot here happened while using Netflix in Firefox 9.0.1.