My computer's hard drive needed to be replaced, so I had to re-install PE4 back in Sept. 2009.
Though the timing isn't right, it sounds like you installed the trial version (30-day trial), of the program. Did you install from your DVD, or from a download file? Did you use your S/N to register it?
Now, there have been reports of PrPro CS4 "reverting" to the trial, when the CS4.1 update was applied. However, that is a totally different program.
You might want to check the Adobe Knowledgebase for "license expired," etc. There might be something there. Adobe did a utility to re-set PrPro CS4, when the problem occurred, but I have not heard of anything for PrE 4, and there were no updates for PrE 4, to the best of my knowledge.
Good luck, and it just might mean a call to Adobe C/S. Customer Service is usually free, where Technical Service is on a for-pay basis.
When I reinstalled it, I did it from the DVD I had. I also used the S/N I originally had.
I don't remember doing any updates to it.
Are you registered with an Adobe ID? (It's probably the same ID as your logon for this forum.)
If so, you should be able to access the registration/activation page. If you have trouble there, you will have the option of contacting a customer service rep live. And they will indeed help you register your product and at no charge. (I've done it myself with older versions of their products.)