Does your installation use project manager? That's the only package I see that requires 'struct' (which I think pulls in tree, set, and so forth).

Are you already running aolserver cvs head or something close to that? The changes to init.tcl were only made recently to my knowledge (Dec '11).

I'll see if I can get the problem to reproduce with project manager. In the meantime, you could try commenting out the errant code - init.tcl:594 which is

::append _import [::list rename [::namespace current]::[::namespace tail $_orig] $_cmnd] \n