This error is just one that drives you crazy. PeopleSoft has been making the move from a 32bit application to a 64bit application. Almost everywhere you will find the that the application runs in 64bit mode, except for in windows. The client application is still a 32-bit client. So if you are using Oracle for example, you need to ensure that the Oracle client software on the windows machine is 32-bit. This is also true with the tuxedo service, when downloading patches make sure that you download the 32-bit patches.
So if you encounter this error, make sure that the 32-bit libraries are installed and are being referred to for the client. DBBIN variable specifically, and if necessary you may need to add the binary path to the add to path variable in the configuration.