Hi Tamar,
This might be caused by the name of your file; if you download a file with the same name twice, your computer might add some info to the title, so the original one is not replaced.
For example, 'Hs_derby_Ensembl_105.bridge' becomes 'Hs_derby_Ensembl_105 (1).bridge' . This ' (1)' can create problems with reading in the file.
As a solution, I would first check the name of the BridgeDb download, and if the situation described above is present, replace ' (1)' with '_2' for example.
If this does not resolve your issues, or if the file name itself is not changed in your situation, you could have a look at the log file.
This can be found in the folder where you have installed PathVisio, and is called 'derby.log' .
This log file should describe error messages for all your actions in PathVisio, which could give us a more detailed understanding of what might be going wrong.
With kind regards,
Denise