#91 Error Opening File on Server

When opening some files via the ftp plugin a dialog pops up: Can not open file "c:\path\to\pluginfolder\user@server.tld\"

### FTP LOG:
01:08:31 > -> RETR /httpdocs/queries/album_query.php
01:08:31 > Response (150): Opening BINARY mode data connection for /httpdocs/queries/album_query.php (85 bytes)
01:08:31 > Error writing data to file, closing the connection
01:08:31 > Response (226): Transfer complete
### LOG END

It looks like every file with an underscore in the name can't be edited with FTP_synchronize.

(I guess the author does not like any one to use underscores in the filename ;-) )

[Anonymous]

Logged In: YES
user_id=1579105
Originator: YES

Checked again, sorry. I don't get it. Other files with underscore in the name (different folder) can be edited normally....

[Nobody/Anonymous]

I'm experiencing the same exact problem with files that have underscores:
/gm/beta3/classes/database/GM/up_GetGroups.php