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Canon 8400F - "Unable to open Twain Source" error message
This looks to be a tricky one. I have two PC's running windows 7 Pro with SP2. One can detect and run Canon Toolbox for scanning, the other does not. When running it states error "Unable to open Twain Source". I have not been able to identify the reason why the windows 7 installation runs differently. I have re-installed the windows 7 (upgrade/repair) on the PC that does not work.
I have read forums that recommend adding a system variable to the path. This does not work. I have tried to compare paths, setting, etc between the machines yet they are the same (at least so far).
Windows scanner and camera properties (c:\program files\windows photo viewer) shows the scanner (Canon 8400F). I ran diagnostics and scanner executes successfully. I select scan profiles and it states "No scanner detected". This is puzzling.
I worked with Canon to delete driver, and re-install (after reboot of course). Re-installed Canon tool box 4.9, the driver is for the windows 7 64 bit. Those seem to install correctly. There seems to be some issue with windows 7 as it seems to see a scanner until you run and then it cannot detect it.
It has puzzled Canon, nothing in the forum so far has a solution and I am puzzled as I have spnet many hours on this. Yet it works on one machine but not the other. I have been un-installing several applications but nothing seems to be in conflict. The driver is shown as installed and ok in device manager.
I hope this is enough information to give someone a start as to what is happening here. I am fairly knowledgable with PC's but this one stumps me. Probably something simple but finding it appears difficult.