I have an vps running on VmWare ESX with Ubuntu 8.04 LTS. It has been running smoothly for the past 3 months, however recently we've notices two strange bugs.

a. The server hangs, today was second time. The nature of the hang is very strange. I can ping to the server server, it sends back response fine. However all other services like sshd, apache, mysql etc do not respond at all. When working,

telnet servername 22
Escape character is '^]'.
SSH-2.0-OpenSSH_5.X Debian-5ubuntu1

And other web services would run fine. When its hung, I can make tcp connections to 22 as well as 80 but receive no response at all.

telnet servername 22
Escape character is '^]'.

How can I debug this problem? Is there any daemons I can run that will periodically log status? Please tell me as to how to proceed with it.

b. The another strange problem is that, of lately I am unable to transfer files larger than around 100KB, smaller files of around 1-2 KB works file.

scp anotherserver:filename .

or

wget http://www.example.com/file

would get stuck. There is still around 6GB of space remaining, so I don't think that is an issue. Any pointers where I should look into?