This is normal.
30 seconds is an ordinary time taken for startup - not just for Ubuntu but also for other Linux based operating
systems, Mac OS X and Windows.
There are some things you can do to improve boot speed. See: How to make Ubuntu boot fast?.
The black screen and blinking cursor is most likely due to having proprietary graphics drivers installed. You can fix this by disabling the drivers but you will lose functionality, like 3D effects. There is a work around for enabling a graphical boot with proprietary drivers: Boot screen in low graphics/text mode.