Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The RBP file type is primarily associated with 'REALbasic' by REAL Software, Inc..
REALbasic is a rapid application development environment that enables developers to create high-quality, native software for Windows, Mac and Linux.
RB was the project extension originally but that is now being used for Ruby development so RBP has been adopted.