if you think it is any antivirus or firewall software blocking requests of your appication
1- check their "blocked program list"
2- you can install Fiddler its free and will show your whatever is being requested from your system, below is the link
http://www.fiddler2.com/fiddler2/[
^]
if fiddler is showing you a request being made from your appication to gmail then
no software is blocking the request.
sorry that was my assumption as i'm not sure the sequence of software will come into the picture. but you can keep it as alternate that your software is making a request. if it is showing your request i think its Gmail and like @nbgangsta said can result in spam. and in that case you can take support from gmail team.
Thanks,
hemant