On my SMP server, I am unable to place redstone or torches onto construction foam, reinforced stone, or rubber tree wood. The server is minecraft 1.1, with IC2 as the only mod.
I can place redstone and torches on vanilla blocks, but apparently not on any IC2 block in SMP. This bug does not appear in SSP for me.
Multicraft's control panel doesn't report any errors, and when I run the server on my local machine (windows7) the cmd window shows no errors when I try to place redstone or torches.