Q: "Invalid Sim" - Apple has, at last, ackowledged the problem

OH! You meant the ASCUA. Yes I read it and you are wrong Finch. Perhaps they changed it since the last time you read it. No big deal Finch. Thanks for your contribution to the ASC. 

I got a 4S for my wife. Had this issue on Orange (UK); phone from them, locked to them, brand new Micro SIM from them, but only appeared after upgrading to the original 5.0.1.

Got really bad, and I phoned Orange who were pretty helpful. They said they'd been in discussion with Apple about the issue for a while and that I should try a couple things (keep it fully charged for a couple days and try a different SIM); if they didn't work to ring back.

Didn't work, rang back, got put through to AppleCare who agreed to send a replacement phone. This has worked flawlessly since it arrived, but it arrived with 5.0 installed. It keeps warning my wife she needs to upgrade to 5.0.1, but I just don't want to. It's working, why risk breaking it?

I'll upgrade it to 5.1 when that arrives, once it has been tested in the wild for a fortnight or so. I couldn't handle the grumbling!!!

Tested the iphone 4s with a new SIM.  Still having those invalid SIM messages.  The only recourse left is to have my unit replaced.

Update: no luck already got an "invalid sim" Message...

I doubt it.  If there is a problem with that, you should have an invalid sim message when you started using the sim.  Instead of having intermittent ones. Based on my observation, my case is that I get the invalid sim problem whenever I passed through an area with weak signal and is unable to recover after even when you are in an area of strong signals.

i am also facing the same problem noservice,seraching and invalid sim from the day i bought Iphone 4s. i changed my sim twice but it didn't work.

Have upgraded to the latest ios plus tried replacement sims, the results are the same. Would you believe that I found out by accident, the iphone 4s displays some signal bars or searching even though there was no sim installed.

Have sent the unit back to the telco for a replacement.  It all points to a hardware issue.

Have the same problem even though I am in an area that supposed to have a strong signal.

I tried all manipulations with sim card (changing, cleaning pins, scotch tape on pins) and upgarded to 5.01 9A406 according to official instruction. It worked for one day and now I still get "sim errors" 2-3 times a day! reboot iphone and sim is OK once again. Looks like it's a sw bug for me and I'm a IT guy with some expirience in such cases.

But what really frustrates me is that officially 5.1 is all about photostream feature with no reference that Apple acknowledges this issue and commits to fix it.

I sent a letter to Samsung PR department with a link to this forum, hope those guys will make buzz in press and Apple will work better.

btw I still love my iPad.

"Apple employees are NOT part of any discussion in the support forums. They are forbidden to participate."

That's not true at all, Lawrence.  Apple employees are encouraged to participate.  It is up to them to identify themselves as an Apple employee, as part of their ID, or not.  Too, an Apple employee only speaks as an individual, and the comments cannot be construed as an official communique or policy.

All Apple forums are regularly mined for data.

We seem to be on the same boat.  I'm also an IT guy and I have been experiencing the things that yu have indicated but much worse.  I get those pesky invalid sim errors about once every 2-3 hours.  I thought that the problem was sw but based on what I acidentally observed, there were network bars even though there was no sim installed.  Based on that, its a hw issue after all.

I think it's a radio module driver issue + interface bug (maybe they tried to make it less responsive thus less disturbing to customer), HW problems are more stable in their simptoms, in this case simple reboot wouldn't help every time.

The only relevant known HW issue that I found is this one: http://wooservers.com/20100710/fixing-iphone-4g-no-sim-installed-problem/  I tried it and it didn't help, some times I got error when my phone is on the table.