Can share files one direction but not the other

I have a desktop wired to a router and a laptop wireless to the same router.
Both machices can use the internet consistently without problems. The
desktop can generally access shared files on the laptop, however the laptop
usually cannot access files on the desktop. I say usually because once in
every 25 tries or so the laptop may access the desktop.
In the event viewer on the laptop I get lots of errors that say the name
"MYHOME" (which is my group name) could not be registered on Interface with
(it lists IP address for laptop) -- machine (lists IP address for desktop)
did not allow the name to be claimed by this machine.
I suspect this is related to my problem. I have sharing enabled on files on
both machines and have firewalls turned off.
I saw one suggestion that in the register, the "restrict anonymous" should
be set to "0" which it is on both machines. However there is something
called "restrict anonymoussam" which is set to "1". I am reluctant to mess
with the register when I don't really know what I'm doing.
Any help will be appreciated.
--
Thanks,

Carl