I noticed that the OpenAL32.dll file in the latest version of Panda1.9.0 is not the same as the OpenAL32.dll file in Panda3D-1.9.0-x64-2014.1.27-503. So I replaced this with the latest version of OpenAL32.dll, and this solved the issue.
I noticed that the OpenAL32.dll file in the latest version of Panda1.9.0 is not the same as the OpenAL32.dll file in Panda3D-1.9.0-x64-2014.1.27-503. So I replaced this with the latest version of OpenAL32.dll, and this solved the issue.