I don`t know if it helps or not but I once had 2 copys of oolite in different locations and when updating AddOns i was updating the wrong file so OXP`s were not working. on deleting the extra copy it worked fine.
Good luck on getting them working it makes a real difference.
One thing you might want to consider is to only add a handful of OXPs at a time. Some of them don't work together, or won't work with your system, or won't work with your version of Oolite. It will be easier to find out which ones are causing trouble if you have only added a few.
Also it is worth checking their ReadMe files in case there are other OXPs that must be installed for them to work.
Just a word of caution - Vista has some strange virtualisation going on in the C:\Program Files directory, so you should only install programs in there that you want to leave well alone. Programs where you want to modify files in the program's directory should not be installed there, as changes you make may not regsiter - instead install to e.g. C:\Games or something similar.
Don't know if this is a problem with Oolite, but it definitely is a problem for various games with fan-made mods.
It has already been a problem with Oolite too and this has been the reason why the default installation folder for the game was changed in v1.73 and later from C:\Program Files\Oolite to C:\Oolite.