xkb, deadkeys and greek

[Yuri Ushakhow]

Hello.

I have such xkb configuration:

     Option    "XkbRules"     "xfree86"
     Option    "XkbModel"     "pc101"
     Option    "XkbLayout"    "us,ru,el"
     Option    "XkbOptions"   "grp:caps_toggle,grp_led:caps"

Problem is, not all greek letters seems to be working. It's possible to 
type alpha, but not alpha with an accent. If I understand right, to add 
accent to a letter, two keys should be used like this:

     ;a  or  :a

However, the letter stays the same regardless of combinations with the 
deadkeys (I call ; and : the deadkeys in this case; sorry if it's wrong).

What could be wrong in my configuration? Or is there some FAQ..?

Thanks in advance.
yura