umtsmon is able to spot problems related to insufficient file/device permissions. This is good, however the "fixing strategy" is somewhat flawed with any 2.6 kernel due to the fact that dev entries are no longer kept statically on the file system, but rather created dynamically at runtime via "udev". Thus, while fixing device permissions does work, it is only of temporary use. A better strategy would be to install a corresponding hal-script that ensures that the entries have the right permissions (user/group) set.
So that whenever a device is hotplugged, the script will directly ensure that the created device files end up having the right permissions.