im attempting a knights of the nine expansion if you will
im trying to use de-isolation (through wrye bash) to change the knights.esp temporarily to an esm for modding purposes
everytime i try and save the mod the CS crashes
ive tried:
a fresh save with no changes made, using de-isolation and oblivion.esm and knights.esm, causes a crash
a fresh mod, no changes only using oblivion.esm, and this does not crash
not using de-isolation, have oblivion.esm and knights.esp as useable files (but not active), and this causes a crash
making knights.esp the active file (no de-isolation) and overwriting this, does not crash (technically mod works this way, but would prefer a separate .esp)

any help as to how to stop the crashing and create a new .esp that reads off the knights.esp as if it were a master file, would be appreciated

Just check the box in front of knight.esp and oblivion.esm (in cs). I think that is what u want to do.

as in when selecting which data files to use?

i think im a bit past that lol

It looks like you'd tried esm mastering, but have you tried http://cs.elderscrolls.com/constwiki/index.php/De-Isolation_Tutorial#ESP_Mastering?

I've never tried it myself, so I'm just tossing it out there.

the method i used was actually ESP mastering not ESM mastering.
based on the descriptions for what i wish to do with this mod on that page, the wrye bash version of esp mastering seemed to be the best option, which is what i have tried.
as far as i can tell it has worked correctly. my main problem is still with the CS on attempting to save the esp.
as i said before i can make a working mod and save it as knights.esp, that works. the only problem is it adds to the official plug in file and requires you to back that up before hand.
a separate esp which adds my new content to the game while still using the base data from knights.esp is what im looking to do, but the CS crash is currenty stopping me from doing so...

Did you try the http://cs.elderscrolls.com/constwiki/index.php/De-Isolation_Tutorial#Esmify_.28bit-flip.29_Method_.28Wrye_Bash.29? I used this on a Battlehorn patch I created and it worked fine. Now I load the CS with OBSE enabled, but that's not necessary. When you open the CS, you need to double-click Oblivion.esm and Knights.esp (so that both are checked off), but don't set either as an active file. You should find Knights.esp is listed at the top with the rest of the esm's because the CS will think it's an esm even though it really isn't. You make your changes and then save them to a new mod file. This should create a new plugin with Oblivion and Knights as masters. Don't forget to flip the Knights.esp back to being an esp before trying to run your mod

If you're trying all this and the CS is still crashing, then the only other thing I can suggest is to try http://cs.elderscrolls.com/constwiki/index.php/TES4Edit_Cleaning_Guide the Knights.esp before trying again. There are a lot of dirty edits in the DLC's and they do cause errors in the CS, so maybe this is causing the CS to crash for you. I don't know if it will help, but there's also this http://cs.elderscrolls.com/constwiki/index.php/CS_Crashes in the CS wiki - basically it just says to follow the instructions on the other page I linked above, but it does make a comment about CS crashes.

Knights was built with a different version of the CS editor than currently avialable..From what I remember.

Make a backup copy of knights.esp,

then use tes4edit and remove the Dialogue Changes from Knights.esp

then use tes4gecko turn that into esm

then you should be able to launch the cs editor and then save your plugin without it complaining and crashing.

Then use tes4gecko to repoint your plugin back to orignial knight.esp

if you need to edit the dialogue good luck you would have to use tes4edit to do that..yuck..

this sounds like the most promising way to fix the problem im having, im not changing any of the stock dialogue so i should be fine, merely adding dialogue to new NPC's im creating.

sorry for double post. i was able to do an automated cleaning of the knights.esp using the CS Wiki guide, but this still has no effect on the crash.
i havent had time to look into how to specifically remove the dialogue changes but from the brief searching i did there wasnt much of a guide on how to do this. if anyone can help me out here it would be appreciated

have also just tried re-installing oblivion to a directory other than program files. the CS crash is STILL occurring.

so in total ive:

reinstalled oblivion to a new directory (not program files)
cleaned the knights.esp with tes4edit
esmify'd knights.esp using wrye bash
attempted a fresh save in the CS using oblivion.esm and knights.esp as master files, without making any changes
(I am running all the programs as administrator)

and the CS still crashes