Thanks Dom, will give all those a go and see what happens. Can't connect to the FTP server from the same network, think it's to do with how I set it up and the port forwarding stuff on the router as well (always says connection refused).

Chances are it's an issue with the wireless rather than the PowerMac being an arse and timing out. So i would do a Google around OSX Network Share Timeouts, there's a fair few hits even with recent versions of Lion. Deleting the firewall files and wireless keychain are a few of the solutions.
Would also check power management, the wireless card could be shutting down causing the timeout.

Saying that, it'd be interesting to see if her MBP will connect locally to the FTP server (or Ping etc) on the PowerMac when she's get the timeout error on the network share.

Yep, the PowerMac is used as an FTP server and for network share, and the box is connected to the network via ethernet cable.

Just thought of something else BTW... I share a printer on my MBP (my MBP is connected via ethernet as well, hers is wireless). Sometimes she can't print to my shared printer and has to do the disabling/enabling of wireless or reboot as well.

My MBP is up to date, not sure on hers though... I'll check tomorrow when she's not using it.

So you have two MBP's and a PowerMac (used for FTP and network shares)? How is the PowerMac connected to the network, wired or wireless? If it's wireless then do a Google around 10.5 and Airport timeouts; from what i remember there was an issue with the connection timing out when using WPA/2 and you had to revert to WEP or no encryption (would test disabling encryption anyway; i've had issues with WPA on 10.6 in the past).

When her MBP fails to connect to the network share, is she able to setup a FTP connection with the PowerMac? Can you ping the PowerMac when a network share connection fails?
What's the situation when you don't login in with a Guest account; does it still timeout?

Guessing the MBP's and PowerMac are all up-to-date?

Edit - If you set up a share on your MBP, can she connect to that when it fails to connect to the PowerMac?

Edit 2 - Might be worth disabling the firewalls on the MBP and PowerMac and seeing if that is the cause (doubtful though).

[Edited on 14-03-2012 by Dom]

the firewalls set up to allow incoming/outgoing shit?

Router firewall?

I dunno.

Yeah the PowerMac is used as both an FTP server and a network share.

Both MBPs can connect to it as a guest, so I don't think it's a user account issue.

so are you using the powermac as a share? if so how is it shared?

My other half's MBP connects to the network wirelessly, mine is connected with ethernet.

Sometimes in Finder when she tries to browse the PowerMac's shared folders it sits there 'connecting' and then after a while it'll timeout. If she disables her WiFi and enables it again it connects fine, but then after a while the connection to the PowerMac will drop off as before.

On mine, I can always browse the PowerMac with no problem at any time.

Should I be adding the IP address of the PowerMac to her MBP's hosts file or something in case there is some DNS server bollocks going on?