There is incorrect platform version information in vmware.xml (inside metadata.zip which is inside the bundle zip file).
Unzip vmware.xml and change "4.0.*" to "4.1.*".
Rezip metadata.zip and add it to the bundle zip. Make sure the paths inside all zip files are the same as before.
Install it on ESXi 4.1 as you have before, it should work.
Cheers,
Daniel