Which version of the Curse Client are you using? I'm not experiencing any system or network problems while updating. (I'm also using Vista Ultimate x64.)
To help with your problem with unidentifiable addons, the easiest thing for you to do is make a list of all your addons. Then rename your Addons folder and make a new empty one. After that you can just install your addons from scratch using the Curse Client. If there are some you can't find hosted on Curse, you can either copy those out of your renamed folder, or download new updated copies from another hosting site.
This sounds like a pain, but I did the same thing myself with over 100 addons and it took less than 15 minutes. (A lot of them were disembedded libraries that the Client installed automatically for me, and several were old versions of libraries that I actually didn't need anymore.)
Edit: If you prefer a text file for your addon list, and your WoW is in the default installation folder for Vista, you can click the Start menu, and in the Start Search box, type cmd to open a command prompt. The following command will give you a list:
dir "C:\Users\Public\Games\World of Warcraft\Interface\AddOns" /A:D /b > "C:\Users\Public\Games\World of Warcraft\Interface\AddOns\AddonList.txt"