I'm using Dopus on an XPSP1 PC, and it's behaving verry oddly.
Even with a dual explorer sitting there with both windows pointing at C:, and Dopus not in focus, the CPU utilisation for dopus.exe cycles between (0%-10%) and around (50% - 80%), which it will then stay at for about 30 seconds, then drops back down to close to 0% for a few minutes, before repeating the cycle. This causes my PC to become extremely sluggish.
I've tried rebooting, quitting Dopus and restarting, and even rebuilding the PC, but it still keeps doing it. Dopus is basicaly unusable on this PC. No other apps on the PC exhibit this behaviour.
I've also searched the forums and tried the suggestions on any topics that are similar (eg: the avi previewing cpu max out topic etc).
Any ideas? 
Run Process Monitor and see what's going on when the CPU usage occurs.
Maybe something is updating files in the directory you are looking at, and this is causing their information to be re-read (or thumbnails re-generated if you're in thumbs mode)? Depending on the filetype (and shell extensions, video codecs, etc. that may be involved) this can use up significant CPU, though for most types of files it isn't significant.
Does the same thing happen if you're pointing at a different directory? What about an empty directory?
One thing about C:\ is that's where your swapfile probably is, and that is being constantly updated. If Opus tries to open it it should fail, but it may also trigger an anti-virus scan of the file (or some other file in C:\ that's being updated), which could take a few seconds and use up CPU (depending on how clever the AV program is). AV scanning, like plugins trying to read file information, will be done by the dopus.exe process but is caused by 3rd party code loaded into that process.
I've finally tracked down the culprit. It seems that if I have the Tortoise SVN client (tortoisesvn.net) installed, and have a Dopus lister at a subversion folder, or any level of parent folder to it, that my CPU utilisation starts the fluctuations. My guess is that because Dopus is trying to get file/folder info, and Tortoise is looking for updates to the folder, it causes this.
Any chance of a fix (it doesn't do this in Explorer)? Alternatively, is there someway I can tell Dopus not to dig for file/folder info for just a specific folder (my subversion root etc) ?
Have you tried changing the TortoiseSVN options so that it doesn't scan inside of child directories?
I've only used TortoiseCVS so the SVN version may be different but in the CVS one there are a couple of options which can cause a lot of activity by triggering recursive scans through large source trees.
In the TortoiseCVS Preferences dialog, Advanced tab, the Folder icon overlays drop-down has three options:
[ul][li]Don't change icon[/li]
[li]Change icon when folder contains changed files (Default)[/li]
[li]Change icon when folder or subfolders contain changed files[/li][/ul]The second option can cause a bit of activity but shouldn't cause a lot (unless you have a huge number of files in one folder, but the third option can really eat resources.
There's also a checkbox for Autoload changed folder icons which is off by default. I'm not certain what that does but I suspect it could slow things down if enabled. (I may be wrong.)