“list index out of bounds” error - BS 11(beta) (UPDATED/RESOLVED)

When error occurs:
On compiling notes into word. The process does not reach the point where the user in asked to open in word.
An error splash box opens with “list index out of bounds” error

The error did not occur on all notes just 1 or 2.

Past Causes - Solutions
The error is reported for earlier versions with possible solutions, e.g. BS 7: http://support.biblioscape.com/node/52
This posting indicated a number of possible causes and solutions - I went through all of those to no effect.
The advice indicated that it may be a problem with the references, including errors in the formatting of reftypes, etc this is very broad but it gave an indication.

Error Tacking
I isolated one of the notes that was causong the problem. It was a large part of a thesis section with over twenty pages.
Copied/pasted smaller sections of the note into a new note and tested compiling.
Some sections worked others didn't.
Isolated a section that didn't work and narrowed down to just a couple of pages and commenced checking the validity of references (eg [Gadamer, 1989 #5923] ) To check that the reference link existed, that the reference type it referred to was valid.

Error Found - solution
I did not have to check much and found a possible cause almost straight away. The formatting of mulitple references. The format for multiple references is [Halliday, 2001 #6020 / Gadamer, 1989 #5923]. I noticed that in one case I had not removed the joining brackets and in another I had missed that there was an extra " ]" bracket at the end as a result of later editing. Not sure which caused the error but I went through checked all the multiple reference formats.

No more error.