We are having problems with our BRD player BDP s300 playing BRD. It will play regular DVD just fine.

Generally speaking, if the Blu-ray player is working properly and has no further wrong codecs or configurations, then it may be possible that your Blu-ray discs are not able to be read by the Blu-ray player.

You can check on this for possible causes and solutions:
Why Won't My Blu-ray Players Play Blu-ray Discs

In most cases, the issue might be with the Java contents on the new Blu-ray discs is making this issues. The Blu-ray technology is developing everyday and adding more and more features to the existing technology. Hence it is required to make the Blu-ray Player up-to-date by installing the latest firmware update available from the manufacturer (who ever it is). Going ahead with the first step, please install the latest firmware update available for the Blu-ray Player.
Please click the following link to get the latest firmware update available for your Blu-ray Player:
http://esupport.sony.com/US/perl/swu-download.pl?upd_id=6170&mdl=BDPS300
You can review the "Important Notes" and "Firmware Update Instructions" on the page to get the instructions to install the firmware update.
If the issue persists after installing the firmware update, the would have been with the disc. Check the disc with another player, try different discs with same player.
If the Blu-ray Player is not at all playing any Blu-ray disc, then it may require service.