Your inter-Vlan routing is handled by your switch or router... it is working at least somewhat correctly because the phones work, but they don't need anything special.
Honestly, from the symptoms it sounds like your gateway address is set incorrectly in the SX-200, but without seeing more details of the network layout it is hard to say for sure. This would explain the inability to use SSH or HTTP access from a different VLAN but it works in the same VLAN, but it doesn't explain the FTP issue...
Did you verify that the ftp server address, username, and password are correct in the 200? You would probably need to change it if you are testing from the Voice VLAN and moving to a different VLAN since your IP address would change... I always use FileZilla server, so I can't speak to CaserFTP or how it works.