automount: Another automount is running

I'm trying to reload NFS mounts on my machine. What has worked in the past is:

sudo dscl .
delete Mounts/
exit
sudo autmount -vc

But now I get the error:

automount: Another automount is running

Doing a

sudo ps -ax | grep automount

shows there's only one process (besides the grep command itself) that contains "automount":

admin% sudo ps -ax | grep -i automount
59770 ??         0:00.01 /usr/sbin/automount
60201 ttys018    0:00.00 grep -i automount

I've tried killing it and rerunning sudo automount -vc and sudo automount -vcu, but no luck.

Has anyone else encountered this error message, or have any ideas on how to fix it?

I'm running Mac OS X 10.10.1 (Yosemite) on my local machine. If it's useful at all, the remote file server is running Mac OS X 10.7.5.