I am finding the same problem, but with Writer.
I run LibreOffice on OpenSuse 12.1 X64, so I don't think this is problem is specific to the Windows version, although it could be something to do with X64.
At first I thought it could be a problem about exporting to .doc format, as I happened to be working on a Word document. So I saved it as .odt and it still takes about 20 secs per save. I'm not sure how long it was taking before, using LibreOffice 3.4.5, but I have a habit of pressing Ctrl-S every few seconds, and it was saving seamlessly, so I'd guess no more than a couple of seconds.
It's not a particularly large document - the odt file is only 130KiB (the doc version was 1.4 MiB). It is a single table covering about 70 pages, but there are no graphics in it.
I just tried a larger document (1.5 MiB, 59 pages with a lot of complex graphics) and saving that took over 40 secs.
Finally I tried starting a new document, typed a couple of sentences in it and saved. It took only a second or so, but if I remember rightly, previously, this would have seemed instantaneous.
Hi @Serg, There are some new 3.6 and 4.0 (beta) builds available for download. Could you please download one of those builds and let us know if you're seeing any speed-ups in opening or saving files? Thanks!
Related question: http://ask.libreoffice.org/en/question/3271/slow-in-spreadsheet-after-update-to-3542/
The new 4.0 is just as excruciatingly slow. I'm losing my temper. Time to consider alternatives.
@imusorka LibreOffice 4.0 is much (times) faster then 3.6. Old Apache OpenOffice 3.4.1 is much faster than even the latest LibreOffice 4.0.
Incidentally, at least in the long past history, some MS Office programs would effectively 'coredump' the application data's memory contents into a file to save it, then read it back in directly into RAM when loading. LibreOffice instead translates application data to a valid, standardized format when writing it out since its beginning (I'm assuming), which adds a step.