I'm having the same problems -- and more -- with my starter kit breadboard. It is difficult even to get jumper wires to go in, and the larger components like pots are simply impossible. The pins will buckle long before they actually go into the sockets.
I took a very close look at the board with strong light and a magnifier, and in my case it seems that the plastic outer layer of the breadboard is not quite aligned with the lower, metallic layer. The holes in the metal layer are offset (not centred) in their plastic "frames" and part of the hole is actually obscured. The offset is along the long axis of the board. This apparently is why I have to insert jumper wires at a 45 degree angle.
The buss bars at the outer edges seem correct, they work properly, but the inner grid of component holes is all misregistered by a tiny amount. I have been wondering if I can forcibly fix this -- like with a warm awl to shove the soft plastic aside -- but not wanting to destroy my (at present) one and only breadboard, I'm a bit reluctant to get violent with it.
I have ordered a couple more breadboards, figuring I just got unlucky and got a defective one. It is very frustrating though, to have this insanely kewl new toy and be prevented from completing even the most beginner-level exercises because the components can't be inserted into the board, period. Also, no socket adapters seem to be provided which might offer a way around the problem (maybe fine square pin to IC-style socket?)