I've spent several hours analysing the log file you sent and looking into some ideas. It's impossible to say if any of these theories are definitely the answer but they all seem worth a try:
[ol][li]After seeing the problem, run Process Explorer (run it as Administrator, i.e. via UAC), push Ctrl+F and then paste the name of the file in. Does it list any processes as having the file open?
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[li]In Opus, turn off Preferences / File Operations / Copy Attributes / Copy metadata (comments, keywords, etc), then fully exit & restart Opus.
(Don't just close all the Opus windows, that isn't enough to exit the program by default. Make sure you select the Exit option, and that dopus.exe is no longer listed in the task manager Process list if you are unsure. Reboot if you are really not sure.)
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[li]The Tabbles software you have seems suspect to me, since it installs a shell extension written in .Net (which is a bad idea), and that extension is loaded near a possibly (though not definitely) suspect part of the log.
Get the latest version of ShellExView and use it to disable anything to do with Tabbles, then fully exit & restart Opus and try again.
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[li]If it still happens, go back to ShellExView, scroll right until you see the "Microsoft" column, then click so the list is sorted by that column. Select all of the non-Microsoft extensions, and disable them all -- except for the Directory Opus ones -- then fully exit & restart Opus and try again.
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[li]Go back to ShellExView and re-enable everything so things are back how they started.
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[li] You've got all three of MalwareBytes, LavaSoft Ad-Aware, and SuperAntiSpyware installed. Did you disable all three of them when you tried before? It still seems very suspicious that this is happening on two filetypes that malware scanners will often spend a long time inspecting for large-sized files.
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[li] The Acronis disk monitor / snapshot tool may be related. Just a hunch, though. If it's easy to disable it, give it a try. If not, don't worry about it.
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[li]From the log, it looks like Windows may be "prefetching" the file. Before Opus even opens it, the special "System" process appears to have the file open. As Opus reads the file, the System process is as well, via code to do with prefetching. It never seems to close the file, either.
This could be normal, and a red herring. Perhaps Windows Vista always does this when buffering large files and I just haven't noticed it before. It seems odd to me, though, and AFAIK the OS buffering a file on behalf of dopus.exe would still generate log entries that only show dopus.exe reading the file, not the System process reading it...
If it is prefetching then Windows has decided this .exe file is one you are likely to use and is preemptively loading the whole thing into memory (or trying to), which may be locking the file.
If you want to try disabling prefetching to test this theory, you'll need to use RegEdit. Go to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters
and change EnablePrefetcher from 3 (three) to 0 (zero), then reboot.
Remember to change it back to 3 and reboot again after testing, as disabling prefetching may reduce performance.
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[li]If you've got anything setup to automatically sync to/from network drives (e.g. Offline Folders), or anything weird like you've setup symbolic links from a directory on your C:\ drive to point to a network share, then that is worth mentioning.[/li][/ol]
If none of that helps then I'm a bit stumped, to be honest.