SmartFTP uses SIZE to detect whether the item is a file or a folder. In your case the server returns a valid size (even though it is zero). However the server should only return the size for a file and not should fail for folders.
There is a chance that we can write a workaround for this particular server. Please post the complete log from the remote browser.
you know what you're I completely forgot we changed our ftp to Cerberus FTP server, and that is when I started experiencing this issue! sorry about that, here is some of the log from the server
[13:42:03] 215 UNIX Type: L8
[13:42:04] Detected Server Type: UNIX
[13:42:04] RTT: 27.666 ms
[13:42:04] 211- Additional features supported include:
[13:42:04] REST STREAM
[13:42:04] AUTH TLS
[13:42:04] AUTH SSL
[13:42:04] LANG EN*
[13:42:04] SITE CHMOD
[13:42:04] SITE PSWD
[13:42:04] 211 End
[13:42:04] Detected Server Software: Serv-U 4.x
[13:42:04] 257 "/" is the current directory
the server software as I said is cerberus ftp, but I'm not sure what else to paste here, and I don't want to publicly paste the whole log, perhaps you can provide an email address to send this to if you need more information?
thanks again for your help!