Exactly the same thing happening to me also in an Acer Aspire One after upgrading the kernel to 2.6.24-23.48. Fortunately an older kernel was left so I can boot and work. From the last comments, I understand that 2.6.24-23.49 in the repository does not solve the problem and we have to wait for 2.6.24-23.50 to fix it.
Exactly the same thing happening to me also in an Acer Aspire One after upgrading the kernel to 2.6.24-23.48. Fortunately an older kernel was left so I can boot and work. From the last comments, I understand that 2.6.24-23.49 in the repository does not solve the problem and we have to wait for 2.6.24-23.50 to fix it.