Access is allowed to, connections are allowed from. The firewall
question seems to have landed in the middle and the wording is quite
confusing as a result.

msgid ""
"With a firewall, you may wish to allow access to specific services on
your "
"computer from others.  Allow access to which services?"

How about

"You can use a firewall to allow access to specific services on your
computer from other computers. Which services, if any, do you wish to
allow access to ?"

[or  "To which services, if any , do you wish to allow access."
although I'm not sure this more correct form will sound correct in
en_US as it does in en_GB]