If you have updated to the latest version of DW then you should most definitely make sure that you are only using the latest version of the extension which will always be available to you from the download area. When you refer to DW CS2 I will assume that you mean DW8 since there was no DW CS2. Since DW8 there have been some significant changes to some of the extensions and the older versions will not function properly in newer versions of DW. The version will always be listed in the download area under the extension. I will pass along your suggestion about re-incorporating the purchased version info and also the code update check feature you discussed.
