Hstore::TooBig ?

I am running a somewhat unfamiliar Ruby automation results app using ActiveRecord to manage the postgres 9.0 backend. During our automation runs we sometimes get bursts of HTTP 500 errors coming back at us, and the Ruby app log shows an Hstore::TooBig error:

Hstore::TooBig (Hstore::TooBig):
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/base.rb:3045:in `attributes_with_quotes'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/base.rb:3036:in `each'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/base.rb:3036:in `attributes_with_quotes'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/base.rb:2934:in `update_without_lock'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/locking/optimistic.rb:81:in `update_without_dirty'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/dirty.rb:146:in `update_without_timestamps'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/timestamp.rb:64:in `update_without_callbacks'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/callbacks.rb:282:in `update'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/base.rb:2927:in `create_or_update_without_callbacks'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/callbacks.rb:250:in `create_or_update'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/base.rb:2594:in `save_without_validation!'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/validations.rb:1100:in `save_without_dirty!'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/dirty.rb:87:in `save_without_transactions!'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/transactions.rb:200:in `save!'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/connection_adapters/abstract/database_statements.rb:136:in `transaction'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/transactions.rb:182:in `transaction'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/transactions.rb:200:in `save!'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/transactions.rb:208:in `rollback_active_record_state!'
vendor/bundle/ruby/1.8/gems/activerecord-2.3.12/lib/active_record/transactions.rb:200:in `save!'
app/helpers/logger_helper.rb:72:in `update_testrun'
app/models/testrun.rb:267:in `transaction_with_isolation_level'
...

I don't quite know where this error is coming from. The ActiveRecord source doesn't seem to have it, and I'm not familiar enough with Rails or ActiveRecord to track definitively whether the failing function is actually performing a DB operation. Moreso I cannot seem to find any mentions (post 9.0 at least) of Hstore size limitations, either key/val pairs (which 8.x docs said was 65k) or the hstore field in its entirety.

So to piece out the questions,
- is there a total size limitation of the hstore field? or is it theoretically large enough (1GB) that it really shouldn't matter?
- is there a string size limitation of each key/val in 9.x, or is it still 65k from 8.x?
- is Hstore::TooBig an error that is likely coming from postgres? or should I continue poking at ActiveRecord or other places?

thanks,

~ john