One of the real problems with the major brokerage firms is that the people actually working for them do not even understand how options work. That will be the cause of 80% of the trouble you get from these firms. Although, IB knows their stuff (somewhat), so I am surprized. Sadly, many of brokers really dont have the foundational financial markets knowledge to suggest much past an overpriced mutual fund. If IB wont let you sell naked put options, why not a put credit spread? Maybe they would be okay with that. http://www.option911.com
IB lets you short naked call and put options, I do it all the time (index options). It is all a question of meeting margin requirements or not, nothing else stands in between being able or not being able to sell naked option positions.
This is also true for equity options. Few days back I sold few out of money PUT expiring 10/09... And I guess only 30% of required cash is blocked from my IB margin (will double check and post correction if that is not correct). OH used to block whole 100% (confirmed).