One last thought after I had a problem with my 350 yesterday. I edited a book removing tables that didn't display correctly and converted them to plain text. But after that the book wouldn't load, the reader was simply stuck in the loading stage and frozen. Triple checked the book, and in Sigil ran the 2 checks and both came out perfect with no errors, so I tried something else.
I'm not sure if the file structure is similar on the T1s, but you might try this if you have similar files. Make copies of your files before making any changes just in case. I opened up the cacheExt.xml and media.xml files and deleted all references to the problem book. One of the files had a LOT of lines from all the bookmarks I was enabling and then disabling while reading, since I was also cleaning up the text somewhat as I read. On the 350, these 2 files are in READER\database\cache\.
Once that was done, I restarted the reader and the book loaded perfectly. I find it hard to believe that you're the only one who's ever managed to brick a Sony and there has to be a way to recover from it.
I'd even try deleting the entire file contents where the info is stored and let the reader re-create them, just be sure you copy the files intact elsewhere first.