I think most of the fault lies with Adobe for two reasons:
1. Extension Manager is a mess
2. Dreamweaver's handling of the cache file
You can get around most of this by remembering to remove an extension before installing a new version, and deleting the cache file after installing new extensions.
Solving problems with Dreamweaver
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Updates are good because it mean bugs are being fixed.
Upgrades are good because we get more goodies. :)