I updated ubuntu 12.04 yesterday. In that update firefox, thunderbird, kernel and snmp packages were updated. After this my login time has increased from 5-10sec to 30-45sec. I surely think it is the snmp packages that are causing trouble. How do i fix those packages to get back my login time...?
You should first get some data, using bootchart ( http://www.freetechie.com/blog/visually-seeing-your-boot-speed-with-bootchart-ubuntu-10-04-lucid-lynx/ ). So you can see what is taking time.
Then, once you have a rough idea, you can either : - disable service that are useless for you - try to see what take time
I would recommend to check before removing anything, of course. Removing snmp is harmless removing something like dkms may let you without working X if you use nvidia driver.
Do not act in hurry :)