I see that you have had no replies.
It is not clear to me whether this hanging on boot of kde4 was a one time event or not.
Does the system now boot normally every time?
I suspect that your problem has to do with the network.
When you power up the machine, it announces itself on the network and if it is not set up for a fixed IP address, it gets a network assigned lease of an IP address. This lease times out and their is a function on the network that keeps track of them and reassigns as needed.
Windows XP trys really hard to become the machine that controls this.
It wants to be the master browser on the network which keeps this list.
When you added your server, things were probably changed and when you logged in via PCLOS, it was having difficulty connecting to the network. There is a good chance that if you had waited long enough, it might have connected ok. But, maybe not.
When you booted with Win7, it announced itself in a way that the network understood and the machine was assigned an IP address.
When you then logged in via KDE4, the network knew what the address of the machine was because it now had a current lease and so was able to connect quickly and all was fine.
So, if you are still having this problem after the machine has been off for a while, you might want to address a query to the network section of this forum.
But be certain to give a bit more information on exactly what this wireless print server actually is and how it is connected to your XP machine.