The Silverlight Team just released an update to Silverlight 4 (4.0.50826.0) which will fix incompatibilities with building and deploying Silverlight projects built on a developer machine that also has LightSwitch Beta 1 installed (SL version 4.0.50630.0). This will also mean that you can now test deploying a LightSwitch Beta 1 application to another machine.
Existing customers will be automatically updated to the latest Silverlight version via Windows Update. Customers who wish to use a Silverlight application for the first time will be directed to the install service (www.microsoft.com/getsilverlight) which will download the appropriate runtime based on their OS and browser.
If you already have installed this latest version of Silverlight on a development machine and then install LightSwitch Beta 1, the latest version of Silverlight will be used so no incompatibilities should exist.
For more information on the release please see: Silverlight 4 service release