Herman,
Yes the reason for that is that you had a previous version of this plugin installed... therfore it already created the cb_phpbbid field in comprofiler... When CB uninstalls a plugin it makes sure that if data is present in the field then it won't delete the field...
Basically everything should work fine... In a future release I hope to change the SQL code that happens during the install so that it will check for that field before trying to insert it... this will mean the use of an install function versus the install SQL that we are using now (and the CB field creation that we used to use)...
You should be good to go... Thought about posting something about the error (warning) this morning but you beat me to it...
We do have a tracker for this as well... (
developer.joomla.org/sf/tracker/do/listTrackers/projects.phpbb_connector/tracker
)
Enjoy,
Greg