Laurent Bugnion reports a small issue with the release of the Windows Phone Developer Tools CTP (April 2010 Refresh) refresh and gives you an advice how to cope with the problem.
The issue is that the Expression Blend Add-in Preview for Windows Phone (April Refresh) is not compatible with Blend 4.0.20408.0, which was the public RC (release candidate).
A few days ago, the Blend team released a fix for an issue that was sometimes causing a crash when Blend was starting up. This new release (V4.0.20421.0) was not very well announced however, and many people (including me) did not install it. After all, Blend did not crash at startup of either of my machines, so I didn’t deem necessary to install yet a new RC.
However, it is now clear that the Windows Phone 7 Add-In needs this latest-and-greatest version to work. If you have Blend 4.0.20408.0, you won’t be able to work with Windows Phone 7 in Blend.