mount -t cifs: "Operation not supported", but can connect via smbclient

At work I encountered a similar problem. moun -t cifs just stopped working. Following mounting a CIFS/SMB resource and looking at the output of demsg, I found that adding the option vers=1.0 did the trick. My command looks like

mount -t cifs //server/folder ./mountpoint -o user=USER,domain=DOMAIN,vers=1.0

After seeing the dmseg and Googling, I found the solution:

One has to add the sec=ntlm option. The problem (feature?) is introduced in recent kernels (I use 3.8.4). I just didn't realize that the problem is kernel-related. So the correct way of mounting is:

sudo mount -t cifs //netgear.local/public /media/mountY -o uid=1000,iocharset=utf8,username="adam",password="password",sec=ntlm