pedb was not able to open the file for reading or determined that the selected file was not a regular file (such as a directory or device).
This typically occurs when manually selecting a new source file for the source window. In this case, the user should check that the filename is valid and the proper permissions are in effect to allow it to be read. If this message occurs because the debugger stopped in a new source file, one may also want to check the source search path using the Source Path window under File on the menu bar. pedb will display no source if it stops in a file it can not read.