kernel 2.6.3 install, lost nics and /dev/usb0

[Paal Marker]

I have done my first change to new kernel. On a rh8 kernel 2.4.18-14  
changed kernel to 2.6.3.  The box is working as firewall, nameserver, 
sambaserver and dhcp server.

New kernel 2.6.3 boots ok,  but I lost several devices. Both nics and 
printer wich was connected to /dev/usb0 are lost.  Booting the old 
kernel gives no problem, and I have to run on that kernel for now. Both 
nics and printer works fine with 2.4.18-14

To manually probe for the nics gives no result, these are both 
3com905-tx nics. 

For the printer concerned, I get the message that /dev/usb0 does not 
excist.

As this is the first time I change kernel on any linux-system, I am a 
little lost here.

Where do I start to solve this? Is what I experience here usually a 
problem when changing to kernel 2.6.3?