http://bugs.winehq.org/show_bug.cgi?id=25494
--- Comment #14 from Nikolay Sivov bunglehead@gmail.com 2011-12-09 15:49:19 CST --- (In reply to comment #11)
Excel 2010 can now also save xlsx files, and it can open the files it saves, but Excel 2007 (in Wine or Windows) can't open files saved by Excel 2010 in Wine; both pop up an error message that the file is corrupt.
Try this now please. Commits 197d41156a1a237eb2073524ec36006d6a26ceaa and b0f704daaf633d8c713c9212a2ab5dd8a4457e7a fix file encoding for me, so now all .docx files are in UTF-8 as they should. Office 2003 + compat. pack opens it without a problem.