I'm sorry to hear that you're having this issue.
I would try calling 800-SAMSUNG and asking to be esclated to the Executive Customer Relations Department and see if you can find resolution there.
I've found hundreds of posts on the internet from angry customers who are trying to resolve the on off issues found on Samsung LCDs purchased within the last year or two. Add me to the list, perhaps. I'm posting this in hopes of finding other people who have had similiar issues, and hopefully resolved them, as well as to draw the attention of the Samsung rep who watches this forum.
My Samsung LCD was purchased in June of 07. Since that time I have had to replace a board due to the HDMI handshake issue, a well documented problem with early batches of this set. Now I have a new problem (perhaps a series of them). My TV takes a long time to power up, generally 10 -20 minutes, and it clicks continuously in cycle, similar to the imfamous "on-off" cycles documented by so many here. I opened up the set to check for bad capacitors, and noticed one which seemed to bulging up. It would appear as though I might have a simple fix then. Just replace it. However, the TV continues to have problems after it has powered up. The HDMI signal will drop out for a second or so repeatedly in intervals of roughly 10 to 20 seconds. Audio does not drop out, only the image.
When I switch the TV to my cable signal (I use an antenna only) I am unable to change the channel and find it very difficult to get any of the menu commands to appear. Changing the source requires great patience. The TV also enters into a cycle where it appears to be powering down entirely (the on/off jingle plays) and coming back on. At this time I can see the broadcast signal, but there are blocking artifacts all over the screen. This cycle runs continuously every several seconds until I unplug the television.
So in summation I have an on/off issue, followed by periodic drop outs on the HDMI, or complete pandamonium on the cable side.
I can't believe a set I've already serviced a year and a half ago is once again falling apart. I wonder if the replacement board was also faulty in addition to the bad capacitors so many are complaining about. I have owned three Samsung LCDs. The first worked fine, the second arrived DOA, and third has been subject to periodic breakdowns. As great as the televisions are in terms of viewing experience, I'm afraid I can never purchase a Samsung product again. I was hoping to keep this television for at least five years. Any assistance in this matter would be appreciated. Thanks. Ryan