Some people have mentioned a problem with the comments here.
I found this solution:
Copy Paste problem on Blogger Solved
Being a newbie to Blogger, I was unable to cut and paste while creating a new post for my blog. I was further stumped when from a friends computer, she was able to cut and paste onto on my blog from her computer. I knew then that it must be something in my settings. After some trial and error I pulled up "create new post" and to the right of the "Title bar" I clicked on "Edit HTML" which was highlighted in white. As soon as I clicked the box the color changed to tan. I was then able to copy and paste with no problem.
and have applied the same fix.
Please let me know if anyone is still having problems.