Sharing Issue Between 2 MacPros on same network

Hi Guys, Im having a strange issue about File Sharing between my 2 MacPros. One has Mountain Lion & other has Lion OS.

Till Last week sharing was working fine & I could control either machine from other one, transfer files etc.

Suddenly since yesterday, whenever I open finder window & click on shared machine in order to connect it, this particular window freezes. Earlier I would get a user name & password window wherein I could enter them & I would get connected & machine would be shown as external disk.

I have done restarts, disk permissions repairs relaunching finder.

I have checked sharing preferances. All is same as earlier.

Kindly advise how can I fix this.

I am currently using Airdrop but its not convinient as I need to keep one finder window continuously open for that.

Thanks