- Check your logs to make sure there's not an error about "Can't connect to X11 window server" - I don't think you would with the latest version, but worth checking anyway. - Check and make sure that the connection to Open Office is working… I imagine it is, if you're getting the large previews… I was having a problem with the open office connection being lost periodically, which I fixed with a cron job that runs every five minutes: http://forums.alfresco.com/en/viewtopic.php?f=47&t=38114
Thank you for taking a look at this problem, however the ref article doesn't answer this issue. For example, the thumbnail of a pdf file would generate with only black channel and not other but when viewing in full preview, all the color present.
Some other people running 64-bit OSes have had trouble with the linked libraries in the included pdf2swf. When pdf2swf is the problem, you should get the opposite problem from the one you have - large previews should fail. However, it's worth checking out.
Check alfresco-global.properties to find the path to pdf2swf - probably {alfresco root}/common/bin/pdf2swf - and just try running it on the command line. Are you getting any errors about loading shared libraries? Several people have found that common/lib/libstdc++.so.5, which should be a link to common/lib/libstdc++.so.5.0.3, is a broken link or a text file. It seems to only happen to people running 64-bit OSes.
Pdf2swf may not be your problem, but maybe something similar happened with one of the other pieces of embedded software. It still sounds to me like your problem is with open office, but I don't mean to beat a dead horse.