My understanding from the report is that they fast aligned the IRS at the gate. The FO being used to entering E for east rather W for west (automation error due to LOT's route structure) put in a position two degrees too far to the east. Due to the lattitude being correct and the longitude relatively close, after probably showing an error message, it appeared to have accepted the data, e.g. no blank screens or warning flags.
At the holding point they realised that something looked wrong with the Nav display and tried to re-enter their position, but then made the situation worse by not reselecting Nav mode. When TOGA was pushed the screens then blanked. This was noticed too late.
The crew told another story about mobile phone interference etc. But as the AAIB notes the recorded data and the pilot's reports do not agree.
It reminds me of a story, which originally I did not fully understand, of a crew many years ago achieving something similar by re-entering the wrong position several times and then having to fly back from Egypt on radar vectors and raw data, after at least getting the attitude data back. Interesting to note that something similar has happened at Easy and probably others too. Hopefully we can all learn from this.