tsearch2 problems / limitations

Hi,

I've successfully added tsearch2 to an existing database and the speedup
of searches is brilliant. I'm now trying to extend this to other parts
of our system.

One of the tables holds reasonable amounts of text, some fields hold up
to 2Mb. When I try and run

UPDATE table SET idxfti=to_tsvector('default', field);

it runs for a while then aborts with the following message

ERROR:  value is too big

Does anyone know what the problem might be here? Does tsearch2 have
configurable (or compilable) settings that could get around this?

Many Thanks,
James