VNC connection from Windows to Mac drops immediately

I had the same issue using Remmina. After setting the Color depth to High color (16 bit), the connection works fine.

Full instructions:

1) Activate screen sharing on Mac OS X:

sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -activate -configure -access -on -configure -allowAccessFor -allUsers -configure -restart -agent -privs -all

2) Connect with remmina, using Mac username and password, and Color depth High color (16 bit)

3) Stop Screen Sharing with:

sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -deactivate -configure -access -off

Reference: https://apple.stackexchange.com/a/30239/57296 and https://apple.stackexchange.com/a/73919/57296

I had a similar issue with a MAC -> PC connection (but without the PuTTY tools)

What I discovered is that the 'Server Type' needs to be implicitly set to the target system or set to 'Other' - Leaving it as 'Automatic' failed to work when connecting between disparate systems.

I can now connect from my iPhone -> PC or MacBook -> PC (and visa-versa) without issue.

I discovered that it's a color issue. I used tightvnc leaving "use 8-bit color" unchecked and setting encoding to Hextile. Got through just fine over an SSH tunnel.