I always delete the cache file before starting any troubleshooting. See if anything here helps:
Solving problems with Dreamweaver
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Make sure you remove old extensions before installing new ones. Make sure that DW is closed when using the Extension Manager. Make sure that you are using the current versions.
You didn't give any OS, DW version info.
10 Tips for getting quick help from a support forum
http://www.ipvac.com/kb/entry/149/