OK - several suggestions:
First: do you get an error report in Zotero (gears menu, Report Error - send error and post ID here).

Second, what happens if you disassemble the dissertation - Do you get an error in all files or just in one?
What happens if you ctr.+A the entire text, and copy it into an empty document - still the same problem?
That's all I can think of atm.

I copied all the text into a new file.

Same OOo error message: "Inadmissible value or data type. Overflow."
Same line highlighted in the file [My Macros & Dialogs].Zotero: Ln 635, Col 60, "mTagStart(nTagIndex) = Len(sResultText)"
I sent an error report to Zotero; the ID is 1882608647.

I'll contact the OOo forum as well, in case anyone there recognises the problem -- though they don't tend to reply anywhere near as quickly or usefully as people here.

Sorry I didn't get back last night -- on top of everything else my internet connection went down. I finally realised what you meant, stopped panicking and started analysing.

I created a bibliography from each of the original individual chapters. No problems -- that rules out dodgy data. I went back to a copy of the whole thesis, deleted the first half, no probs, deleted the second half, no probs, tried a copy of a copy of the whole thing: error. Deleted photos, diagrams, tables in case Zotero doesn't like non-textual stuff: error. So it seems the quality of the content isn't the problem. Could it be the quantity? I deleted the first third, no probs, deleted the last third, no probs, so it can handle c. 200 pages, so text length seems unlikely to be an issue. But that prompted a thought.

I went through the entire 288 pages deleting large blocks of text that didn't have any citations in them. Eventually I ended up with just 50 pages of text but with all the citations. Tried to create a biblio: error. Deleted 10 pages: error. Deleted another five pages: no probs.

Conclusion: OOo &/or Zotero can handle a long text file with no difficulties, but has a limit on the number of citations (or perhaps the number of entries in the biblio) it can handle when creating a bibliography. (And no, I haven't counted them -- yet.)

I went back to the whole thesis and experimented until I could successfully create a biblio from the largest number of chapters, 3-8, then did the same for 1-2. Then printed them both out and went through them with a red pen, deleting dupes and sorting out the inevitable confusions over 1986a, 1986b, 1986c etc. Then, not having any alphabetical file merging s/w that I know of (25 years ago I could have written a program in Unix shell language in 5 minutes to do it!) I put the two files side by side on screen and spent two hours laboriously copying from one to the other, one entry at a time, finishing well after midnight. But now I have a bibliography for the whole thesis: Joy.

I've gone into this much detail for two reasons: 1. to help anyone else who gets into the same scary situation with time running out; and 2. so that the programmers at both OOo and Zotero are aware of the problem and can maybe attempt to fix it in the next release. (If they haven't already; I'm aware that I'm not using the most recent version of Zotero, because it upgraded part way through my work and it didn't seem wise to change horses mid-stream.)

Thanks again for your help, and for calming me down when I was panicking.

David

The celebration will have to wait until after the viva (I hope) in a few months' time -- but yes, once I've printed, bound and submitted the thesis I'll have time to look through the problem again, and report back.