I also have a Dell Inspiron 1545 and my keyboard is acting in a wierd way. Press any key and nothing in one instance and a little later it will type the correct characters for a few seconds then nothing. I have checked all the configs, re-installed the driver, used safe mode, and finally connected USB keyboard that also did not work yet in did in my other Inspiron Laptop. I have tried re-installing Vista which is hard if the keyboard does not work. Amazingly by holding down both the left and right shift keys you can sometimes generate the correct characters. I then resorted to check with Dell who suggested removing the keyboard to check for and problems there, which I did to no avail. Need to send back under warranty but currently 7000 miles away from where I bought it.
Changing the keyboard is relatively simple and Dell have probably already walked you thru it. I'm sure they would rather send you a new keyboard than have to ship back your computer to you. It may not be the solution, but worth a try.
You are correct, they did agree to send one to my home address in the UK, except I am currently in the Philippines and they were not prepared to send here. Fortunately I have found someone here that has been able to fix the keyboard and now the laptop is wroking okay. Looking around the various problems that have been posted re the 1545 keyboards it is a wonder Dell are still selling them. Thanks