Binabik: Sorry i did not reply yesterday (Birthday drink and everything lol).

Did you try Exporting your Bookmarks to your Desktop and importing from there ?
If it is speed you are looking for Mozilla do a Application (that is also a Firefox Add-on as well) called Prism. It is faster than any browser as it runs a website as an application as such (for want of complicated terms lol). You get nothing else apart from the webpage, no Add-ons, no forward/backwards, Bookmark buttons etc..etc....

If you fancy using it, i would suggest downloading the Add-on version into Firefox. Once installed, just click Tools on any website you use (or spend a lot of time at) and in the pop-up menu you select 'Convert website to application'. Give it a name when the page pops up, and it will create a Icon on your desktop.............. instant speed lol

All this said, try to get the Bookmarks sorted as well lol