Problem 9:
The input is invalid if it is less than 'A' OR greater than 'Z', and you want your loop to keep going until you have valid input. Look carefully at the conditions involving chrLetter. Also, instead of duplicating the logic, I would consider either setting a flag when valid input is found or using break to exit the loop.
You're also going to run into an issue when entering invalid inputs in which you are prompted twice. This is because scanf reads the \n when you hit enter as the next character. You can use getchar() instead, or prepend a space to your format string so that scanf consumes the whitespace before the character each time. Also watch for /n vs \n in your printf's.
Problem 10:
Try printing out intCount each loop or using a debugger to see what is going on. Once intCount gets to 8, what do you want to happen? Currently, there is nothing to cause the loop to terminate. Also, while it doesn't matter in this case, when waiting for a value to pass a threshold, I prefer to check if the value is greater than/equal to the threshold, as opposed to just equal to. That way, if intCount somehow got to 9, your loop would still exit as intended.
