I have a lot of trouble with multitasking, especially at work. Sometimes I have to help customers on the sales floor while getting a project done in a timely manner. It would be a lot easier for me to just do one or the other, as the quality of my work with each goes up when I do one or the other, and goes down when I have to multitask them. The funny thing is, they all know I'm autistic, yet still expect me to do it as well as everyone else.
Interestingly enough, there are some things I can multitask well enough, such as cleaning my room and/or doing other chores while my laundry is in the wash, then putting the laundry in the dryer, then finishing the chore or starting the next one, though this might be a result of making a routine out of these things rather than strong multitasking ability.
Things like eating while watching tv, and typing this post while listening to my music, I have no problem with. I can't read newsscrolls on the bottom of the tv and listen to it at the same time, though.