Basicly the only thing you CAN'T recover from are a completely broken firmware files. (Eg. A corrupted key PRX).

Or, if you bricked using a font or something like that, you could place the X-flash files inside the "PSP/GAME/UPDATE" folder and use the option to flash the original Sony fonts.

Though, if a Sony update is not an option, try using a custom updater, such as the 2.71 SE installer, then using the generic downgrader to return to v1.50!

If there's no way to fix it using an update, then you just need to find a way around it!