This error usually happens when using a PowerPC based Macintosh computer.  Try installing the latest DSLR Server by clicking here.
This update addresses the 0000003D error code that PowerPC users are getting with the Server.
If you are using an Intel-based Mac or a Windows operating system, you do not need this update as it [...]

If you are using a Nikon DSLR we are limited by their SDK to save only to the computer.  We do not get options to save to both the camera and computer.

This is a known issue, mainly due to the speed that auto-bracketing shoots at the client cannot update fast enough to reflect what the camera is doing.

Since this product is purchased through the Apple iTunes store, the return must be requested from iTunes support. To contact Apple iTunes support, please click here.
Here is the onOne Software return policy:
Products purchased directly from onOne software, including electronic downloads and products delivered physically, come with a 30-day money back guarantee. During this period you [...]

Normally DSLR Camera Remote will attempt to auto-focus the camera when the Fire button is pressed. For this to work, just like on the camera, the lens needs to be set to AF and LiveView should not be engaged. If the camera is in this condition and it is unable to focus you will get [...]

This can happen with certain models of camera if the Review time for Live View has been set to Hold.  If you have set your camera’s Live View review time to be Hold you will want to set it to one of the timed review options like 2 or 4 seconds.

The following cameras do not support shooting in bulb mode with DSLR Camera Remote. Unfortunately there is no way for us to add this functionality, as it is a limitation of the Canon EOS SDK which our product is build on top of.
1D Mark II
1Ds Mark II
1D Mark IIn
20D
30D
5D
Rebel XT/350D/Kiss Digital N
Rebel XTi/400D/Kiss Digital X

This error can be due to not having .Net 3.5 installed.  You will want to download and install the .Net 3.5 Framework installer from the Microsoft site.
Please copy & paste this URL into your web browser.  Once .Net 3.5 has been installed you will be able to use the DSLR Remote Server.
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=333325fd-ae52-4e35-b531-508d977d32a6