Okay, let me try and answer a few of the questions. Please understand that I don't work for Devellion/CubeCart, but merely volunteer moderate on here, and have a large number of store licenses for ourselves & customers.
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I was unable to access my admin area, my webpage had an error due to the key.php file not being able to update
The CubeCart server move, which started just over 2 weeks ago,
shouldn't have affected anyones stores. The move to the 1st of the new servers (as it became) went smoothly and everything was running fine, however as the licensing system in CubeCart calls home every two weeks, within a few days, reports started coming in that some stores couldn't access the licensing server. This, after much MUCH dialogue between CubeCart and the server provider, was found to be being caused by a firewall outside of CubeCarts control, which the Datacentre didn't seem to want to do much to help about.
As their senior admins couldn't figure out a way to help CubeCart achieve what it needed, CC took the decision to move server hosts to a new datacentre, where there weren't these firewall issues. This move had more problems owing to the "highgly recommended" server management company which CubeCart rightly put their trust in.
Once all the issues were sorted stores are now able to talk to the licensing server without issue.
Had the server move gone as expected, no-one would ever have noticed. Sotres would have picked up the new IP address of the licensing server and carried on away validating every two weeks.
This two-week call-home is to allow, as a lot of software vendors do, the control to disable a license, should the payment be found fraudulent after the order has been processed, etc etc. It's an important function to maintain the licensing model for CubeCart, so that the developing company earn their revenue to pay the developers to keep on, well, developing.
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what if one day cubecart.com decides to close up shop
As this information is in the public domain, I don't mind telling you that Devellion Ltd, the company behind CubeCart is extremely Financially robust. I certainly don't forsee *any* problems, and if I did, with a lot of business to protect (mine + my customers) I wouldn't be putting my trust in Devellion. I know the guys there very well, and they work extremely hard to produce CubeCart and support its many diverse users.
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why it needs to keep regenerating a key.php file, especially since it did it the first time when it's installed.
As I've said above, the local key.php is a way to stop the store having to call-home every time you use it. It's designed to seamlessly sit in the background, checking occasionally you're still licensed.
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Also what other areas are dependant on cubecart.com?
Only the Admininistration panel is dependant on the licensing server. In case there are ever server issues (which I believe there wont be from now on) then the idea is that the front end of the shop isn't affected, so that people can still browse and order from your store. No information is ever lost.
The only other thing dependant on cubecart.com is the version check on the admin home page, but this wont cause a fatal issue if it cant work, so no worries there. And the RSS feed if you still have it pointed to the cubecart.com one. Again, its non critical so wouldn't cause you any issues.
Hope this goes some way to explaining the situation.