Ok, so today I tried to load XSI, and when I tried to orbit the camera, it wouldn't ordit unless I held down the "O" key, where as normally I could just press it. It also does this with rotate, pan and zoom...

Another problem came present.
I cannot multi select objects any more when I hold down the mouse button unless I hold down ctrl, normally I can just hold down the mouse button and it selects...

last problem is, normally I press the little key button to add keyframes for animations, now it won't even let me add keyframes like that. how do I repair my keyboard configuration.
and is there any alternative way to add keyframes?

firstly, you need to have a transformer active to set a keyframe, like pressing X, C or V and then setting the key you want to set. as for the orbit thing, i dunno, i alwasy held mine since i thought it was faster since when i let go of the key it would turn the tool off, i like it better that way. ctrl and shift in almost every windows application is grow selection, where you clicking and dragging a box over the selection or where you growing selection without holding ctrl and shift and just simply clicking on one thing at a time and it added to selection. if so thats something that kinda slows you down as well since mod tools has its settings like that and it was something i always couldnt stand.

Tried to reset your configurations?

usually such problems are dealt with under Preferences. Sometimes they actually deactivate a configuration even though it's checked. Don't ask me why, but it usually scares people off who haven't seen this happen before