Yes, You can upgrade from ESXi 5.0 to 5.5. Make sure that your server currently running on ESXi 5.0 is Compatible with ESXi 5.5 by verifying at VMware compatibility Guide first.
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It seems that the log just holds the last update comitted to the ESXi
What about the previous updagrades/updates?
In my case, I get the information fromt the last patch applied, not the upgrade from 5 to 5.5