Is it lines or waves that you see?
Both, but waves concerns much more to me.
He had an issue where there were he could see some lines particulary on the left side of the screen
And yes, I can confirm this. It is noticeable under gray background. Lines are slightly more separate on the left part tan the right. I cannot distinguish them on the right part. But this is not my real problem, the problem is I also see waves (yes, waves) running from bottom to top when panel is warmed up (about 45-60 minutes turned on). If I switch off the monitor, when it's cool and it is turned on again, no waves appear at all.
I can confirm is a problem of my panel too, because in another house occurs the same.
NEC denies to repair the monitor again. They're convinced is a customer problem, not a product problem (?)
Thanks again Tamlin, I'm realy desperate with this issue. Because I've had several replacements due to issues (3 in total), I'm thinking seriously about buying a NEC 2490WUXi and sell the 2690. The 2490WUXi is already selling on Europe and, according to ToastyX, this monitor has less problems with quality issues than 2690.