HDMI not working since update

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http://askubuntu.com – I am new to using Ubuntu and I have no idea why this happens; Before used the HDMI output to a Sharp TV. Worked perfectly with Ubuntu 11.10, upgraded to Ubuntu 12.04 (Linux 3.2.0-25-generic) and stopped working, the display connected via HDMI it says "incompatible signal, check the device configuration," which never appeared in 11.10. I use a Dell Inspiron 1525 Laptop. thanks EDIT: Boot from GRUB with the option to earlier versions, which I think works with different KERNEL, well, the point is that in this version of Ubuntu Linux 3.0.0-21-generic, the HDMI those works perfectly. It is not a (HowTos)