Liteon 24x problem

I had this burner since they first came out in the UK, it started to play up where in it would take ages to spin up to 16x -24x speed to burn sometimes 4-5 mins or it would time out, but 12x or lower it would work fine. It was in warranty but it would have cost to much to send to liteon, so I took it apart and cleaned the lens with compressed air, as read somewhere you could clean the lense this way. This didn’t cure the problem is there anything else that I could possibly do ? It also ssems to have problems reading at higher speeds but at lower speeds all is fine.

Oh I had a search on the forum for similar problem but I couldn’t find any, but if there is a thread I miss could someone not flame me and point me to it.

Many thanks in advance.