bigmemory for dataframes?

Hi Folks,

I've been bumping my head against the 4GB limit for 32-bit R.  I can't
go to 64-bit R due to package compatibility issues (ROBDC - possible but
painful, xlsReadWrite - not possible, and others).  I have a number of
big dataframes whose columns all sorts of data types - factor,
character, integer, etc.  I run and save models that keep copies of the
modeled data inside the model objects as well (mle2 objects, to be
specific).

I'm searching for a way to cache some of these dataframes and objects to
virtual memory (I think I'm using the right terminology...).  I've read
around, and while bigmemory and ff and the like would likely suit my
purposes if I were just dealing with numeric matricies, I'm dealing with
dataframes and objects.

Any thoughts would be greatly appreciated!

Thanks,
Allie