Installation and invalid access to fat

I tried to install ubuntu on my hp laptop. The installation stopped when it arrived at "Searching for other os". In particular the error was the following:
ubuntu keel: [some numbers] FAT - fs(sda1): error invalid access to FAT
same message with different numbers
ubuntu ubiquity: find ... Input/output error

My first partition is a 400MB unallocated partition which I caot merge with my unallocated space.
I then created a new volume and tried to install ubuntu again. In that case, the sda mention in the keel message was sda2