This error message comes up when you try to open a damaged Soundstorm program (part of the nVIDIA NForce software group):
'Incorrect size returned during FXMANAGER_ALLOCATE'
The FXMANAGER_ALLOCATE error occurs when you try to open the Nforce Control Panel and then Control Panel trys to open the soundstorm program (C:\WINDOWS\system32\sndstorm.exe - location of file for Windows XP) and fails, producing the error message.
This damaged sndstorm.exe program needs to deleted and reinstalled. The only effective way to do this is completely remove the NForce Drivers from your PC and then reinstall them from the nVidia Software Disc, a manufacturers driver folder on your PC (probably located at the root of your C drive) or from the nVidia web site