I believe 6.1.4 source poofed with bounty source.
Also mud had a system crash or he accidentally deleted the files the brain forgets these things easily.
So it is what it is I suppose I don't believe I religiously retrieved source versions of the plugin like I should have. In fact I'll have to look if I have any source (sigh). Looks like I only have 6.1.1 beta (ick).
Erstwhile here are my suggestions. Religious backups <--

I recomend daily backups myself (I make automatic ones that are date and time branded for serious projects). Back up to a seperate machine on a network or a USB drive. Doesn't matter. WRite a script to do this (I did it's not hard) and put it in your scheduler in windows. This means you'll have a lot of backups of the same stuff, those you can delete ( I do) if you don't update for a week. However it's backed up and cheap insurance.
Daily backups are also good for making mistakes and finding them fast. Use beyond compare or similiar utility to do comparisons to see what you might have hosed.
Yes I do have experience, I work on things that have to work or someone dies, quite a bit of responsibility there. So my backups are religious every change has to be carefully thought through and documented. It's not fun in fact it's kind of tedious. (sigh)
Erstwhile if you don't wish to redo something or find out what you need to unfix then use the backup method I metnioned. You may also wish to start adding doxygen commenting to the source. If you need help with this ask me, I've done some extensive use of doxygen. It works very well but you have to use it and understand how it works.
Releases need to be very carefully documented as well. IE what is changed and when. This isn't just for you but for the next person in lines. If you can move the project to source forge and use the SVN clients with it regularly. Keep several branchs maintained and keep a local set of backups on your back up HD.
I can help with some commenting and some doxygen. Do not get the idea that source code can be self documenting, personal experience has shown that this doesn't work well. I've also found a lot of other people concluded the same (wow hehehe). If you need some doxygen additions let me help you. I've used it for 18 months, it works, if you know how to use it. Also it gives you an amazing view of your code how it flows etc. This is extremely important if you are trying to figure what is going on in your code. Of course some of the call diagrams can drive you nuts.
Again if you need help ask, I can help some, not in terms of coding but helping documenting the code yes. That at least I have a lot more experience with than that nuts and bolts of the plugin.
As for 6.1.4 call it gone, mostly because the amount of work to find out what was done is greater than the amount of work needed to redo it.
I also suggest getting some sort of over all documentation on how the plugin works (not like Zilmer's spec), in terms of what data is loaded, when it is loaded and what it is used for. It's boring stuff I know but it will reveal errors in the methods used likely. That is a good thing I always say.
That's the best I can do. There were some interesting plans brewing as well but what is more important is to have the code with commenting and documentation then more people can work on it. That's my 2 cents. In fact documentation is probably more important than fixing bugs. It will make bug fixing much easier in the long run. Not sure how long or how much work it is.
Most importantly have fun.
Perhaps sitting down and having a strategy meeting 'it's an expression' on how to proceed will help you resolve what to do first? Having direction helps.
I do have a source forge account as well.
The source was last viewed on 8-20-2007 (wow long time ago). I don't believe I have anything other than binaries otherwise. I can't remember if I had trouble getting the source or something equally silly.
Cyb