Yes. It probably has to do with the wrong path to the system modules. Actually, that /system/lib/modules path is pretty common. So you're probably not checking the option to load via insmod - double check the path to make sure its correct. Also try (via terminal emulator) cd /system/lib/modules && insmod cifs.ko
And then lsmod (if you have busybox set up) to verify. On second thought, cifsmanager has sort of a built in lsmod via clicking "about" and then "modules". You should see bcm4329 (or dhd, I don't know what its called on the Xoom exactly) and if the cifs module is correctly loaded - you should also see cifs loaded.