Recently, my Firefox browser started loading without the extensions I've installed. I run my Firefox browser off of my 4GB Cruzer using the PortableApps suite.
When Firefox loaded, it would load without a single extension, but when I opened the "add-ins" box, it listed all of my extensions.
Here is the thread where I found my particular solution. I was able to get Firefox to load my extensions again by modifying the files within my Firefox profile (find it in you user account appdata folder). I deleted extensions.cache, extensions.ini and extensions.rdf. When I started Firefox the next time, it regenerated these files using the extensions that were in my profile (folders like {2fa4ed95-0317-4c6a-a74c-5f3e3912c1f9}).
Problem solved for me. I did take notice that Firefox is blazing fast on start-up. . . until I load a ton of extensions. With the number of extensions I have, it's more like Visual Studio since I'm loading up a whole suite of web development tools. Firefox is just as much a web IDE as Visual Studio - including the RAM usage.