virtualenv / virtualenvwrapper resetting $PATH?

[Nan]

I just installed virtualenv and virtualenvwrapper on an OS X machine
(10.6).  My ~/.bash_login adds a few paths to the $PATH environment
variable, but upon activating a virtualenv with "workon", those paths
go missing from $PATH (and are not restored when I deactivate the
virtualenv either).

Any suggestions as to what I might be doing wrong?

Thanks!