I open files of a site in Magento 1.9 through Notepad++ with plugin for FTP connection. I don't try to download system.log file. The error is the following:
Download of /balmain/var/log/system.log failed
Can you help me, please?
In my experience, Magento log files can get very large. Up to 300 MB or higher if they're not cleaned up. The extension for Notepad++ FTP you are using may have problems with large text files like this.
I use Brackets often, and wasn't able to open a log file because it was over the maximum file size. I was able to open this large .log file in Notepad++ and Notepad though. This is why I think the FTP extension is at fault.
I highly recommend downloading the log file to your desktop via FTP, and then opening in Notepad++ from your desktop. Filezilla is a good free FTP program that's easy to set up, if you don't already have one.
Good luck!