Strange. I use ClassicWB 3.x made from OS3.9 on my A4000 and I also use a PC keyboard...
Have you tried another keyboard? Also, try the DEVS draw and look at what keymaps are available and make sure you have the correct one for your country in there.
I'm actually formatting a PFS3 80GB hard drive on my PC using WinUAE and I'm going to copy ClassicWB 3.x onto that and use it on my A4000. I'll post here if I have any issues.