What version of NetBSD are you running?  The "No buffer space
available" is a side effect of uvm's tendency to fragment memory into sizes
smaller than the umass driver needs to do its thing.  However, NetBSD 3.0
and 2.1, as well as 2.0.2, I think that's right, have patches to work
around this annoyance.  Alternatively, rebooting your box with the reader
plugged in ought to get it up and running.  Incidentally, it will probably
show up as multiple SCSI disks, one for each type of media the thing
supports.
For example, I have one here that does a google of media, here's how it
probes:

...
umass0 at uhub0 port 1 configuration 1 interface 0
umass0: ICSI USB2.0 Card Reader, rev 2.00/1.6e, addr 2
umass0: using SCSI over Bulk-Only
scsibus0 at umass0: 2 targets, 4 luns per target
sd0 at scsibus0 target 0 lun 0: <ICSI, IC1210        CF, 1.6E> disk removable
sd0: drive offline
sd1 at scsibus0 target 0 lun 1: <ICSI, IC1210        MS, 1.6E> disk removable
sd1: drive offline
sd2 at scsibus0 target 0 lun 2: <ICSI, IC1210    MMC/SD, 1.6E> disk removable
sd2: drive offline
sd3 at scsibus0 target 0 lun 3: <ICSI, IC1210        SM, 1.6E> disk removable
sd3: drive offline
...

-Brian