CS5 file hanging CS6 when modifying styles

Question

Windows 7, InDesign CS6 8.01
I was working on a file of about 91 pages with a lot of tables in CS5 last week. We just got updated to CS6 this week, and the file seemed to be working fine. I decided I wasn't happy with the look of the tables, so I went in to the table style, changed the colour of the row fills, and as soon as I clicked on "Preview" I got the spinning blue circle. Only way out was to end program.
Since then I have tried the following:
* Change colour without previewing (hangs)
* Re-import CS5 document into CS6, try again (hangs)
* Open file in CS5 on another computer (as it was uninstalled on mine) and try the same thing (fine)
* Export it out to IDML from CS5, and import that into CS6 (fine). Try changing style (hangs)
* Try changing the colour of a font in a paragraph style (hangs)
* Try changing the font of a paragraph style (fine)
* Open the CS6 document that was casuing all the trouble on another machine with CS6 (doesn't display, then hangs)
* Open the CS5 IDML on the other computer (fine) then try the table style change (hangs)
* On the original computer, re-import the table styles from a previous version (fine) then attempt change (hangs)
* Duplicate the table style, change the colour in the style (fine, but not applied to anything), then delete original style, replacing with new one (hangs)
I'm at a loss here, as my usual solution to weirdness is to go the IDML route as I thought that re-built the file anew. Doesn't seem to want to play along though.
Any suggestions?

Answer 1

Thanks for your reply Peter. I hadn't thought about the tagged text route, probably because I've never had a use for tagged text!
I gave it a go, exporting the whole of the troublesome section as tagged text. Placing it back in to a new InDesign document with automatic text flow on, I got the same crash/spinny-wheel-causing-me-to-end-task. I tried it again, but this time turned off autoflow and did it page by page, noting the point that it would crash. Next time, I cut out the table that the crash would occur on when I got to it (the crash would happen as soon as I clicked the out port), pasted it on the side, made a note of where it went and continued to place the rest of the story without a hitch. I could change the table style in this document no problem.
I pasted the troublesome table back in, tried to change the table style and got the crash. Right, getting somewhere.
I opened up the previous template, and put back in the section that wasn't causing the problems (everything without the dodgy table). I could change the style fine. I then made a new document, and pasted only the bad table, figuring that it would crash when I went to change the style. However, I could change the table style just fine!
So, figuring that it was all ok now, I copied the table, pasted it in with everything else, went to modify the style and... spinny ball.
Finally, I converted the table to text, pasted it into the main document, and converted it back to a table. So far, so good. I'll update again if I run into any more problems.
Realistically I could have set the thing again in the time it's taken me to troubleshoot this, but I'm a little scared that this happened at all with a document that works just fine in CS5!