ESXi 5 VM Putty session hangs, vSphere client timing out

First of all I believe this is a ESXi issue but let me know if you have seen this. It started about a year ago when I noticed occasionally when I putty via SSH to my VM guests, if I do anything that makes it to display a lot of things at once, the session will hang and I have to start a new one quite often only to find the same behaviour. What I meant by display a lot of things can be any of the following:
1) tail -f filename
2) Paste a long command
3) less filename

If I type in one character at a time this won't happen. I tried searching online and it always point me to flow control settings and the various suggestions I've tried have never been able to resolve the issue.

Since last week, I've noticed I'm not able to connect to my POP3 server from Outlook (it's timing out from Outlook's perspective).

Today I tried to connect to the ESXi via vSphere client and it gives me a time out also. Exact behavior and error I saw is similar to the one posted at the following URL but the suggested technique also failed to resolve the issue. http://davidcocke.blogspot.hk/2012/02/unable-to-login-with-vsphere-client.html

Has anyone experienced this before? Any suggestions on how to troubleshoot this?