Can't connect to iMac with MBP

Hi everyone, I have a problem connecting to Mac "A" (Running OSX 10.5.8) from Mac "B" (Running OSX 10.6.7).

For example, when I'm using Mac "B" and I click on "xxx's Mac A" in the shared pane, in the sidebar in finder, it says that it has failed to connect.

But, here's the weird thing. When i'm on Mac "A", trying to connect to Mac "B", it does connect (file sharing/screen share)

Can someone help me connect to Mac "A" from Mac "B"

Btw, both of the computers are on the same network, and i've also tried connecting via Finder>Go>Connect to Server>"ip address"

Is it maybe a problem because i am using 2 different releases of OSX?

Thanks a lot

 

Thanks for the fast reply, and yes the relevant sharing preferences are all set. (File sharing & Screen Sharing)

 

Thanks for the reply not silly at all.

In finder, when i clock "connect as" it doesnt to anything!! but the real problem is that Mac B wont connect to Mac A at all. When i try to connect it comes up with a "Connection Failed" message, which says "This server may not exist or is unavailable at this time. Check the server name, or IP Address, check your network connection, then try again"

Tried all of those things, but it just wont connect

 

Ok i've had a look at all the settings on both the computer's system settings. This means that it must be a network problem, or that OSX 10.5 & .6 arent playing too nicely together, any ideas?