A few Delphi developers I know have been hit by licensing errors... because of a new protection feature in XE3, documented in the release notes. Given I received 3 different reports of this problem by 3 different developers, I felt it is worth pointing it out.
As you can see in the Release Notes for XE3 under the header "Do not install extraneous files in \bin directories" you should not install any DLL or package in the bin and bin64 folders of the main Delphi (or C++Builder) program directory. This is because the DLLs and packages (BPL) in that folder are checked for the original Embarcadero signed version, to avoid developers (or malicious third parties) to temper with the IDE and its licensing.
As the release notes indicate, A license validation error will occur. Given this error, however, the IDE will prompt you to register, to no avail, as the issue is not a missing registration. I know, this can be confusing and time wasting. But if you know about it, it becomes a no-brainer.
PS. Please do not comment with a tirade about the licensing protection, how annoying it is, how useless it is and all the rest. Yes it can be a bit annoying to legitimate users, but it is NOT useless. I have personally sold licenses because the IDE was informing users... they were "sharing" the licenses they had.