plextor 8320 (or something like that)

[kha5693399]

My plextor drive (8x4x32) used to burn at 8x beautifully. But now, it will only burn at 4x max without having data loss or write errors. I have had it for about a year, but just in the last 4-6 months have I started to burn at 8x- how convenient that my warranty just expired!! Any help as to why?? The same thing happenned with my phillips 4x4x24 last year. Is it just me, or is there a pattern emerging here???