I'm happy to report that inbetween starting this topic and getting any replies, I opened my Amiga A1200 case (which Has been left without screws for some time now), pulled the keyboard out of its usual position, placing it at the back and upside down, but without disconnecting it, had a look at my capicitors which all seem fine, then I put everything back together and started to test it by playing Civilization again. I wasn't sure which of my three versions I should try, but I ended up playing the AGA German language version, although there are lots of mistakes and English words in the translation! I found that I was able to play from 4000BC right the way through to about 2050AD without it crashing, even though I was hitting the cursor right key and the 2 key on the numeric pad as hard as possible! At that stage in the game, I had almost my whole empire overrun by another empire which started a war with me just because I refused to keep paying them tribute! Eventually, I had only two cities left in a far flung overseas outpost and a population of only 80,000. After that, I decided to quit and reload a saved game. I found out that the saved game maps weren't corrupted like the ones I saved before, then I was able to carry on playing from earlier dates without crashing.
As for some of your questions and suggestions, my Amiga A1200 is PAL, my total RAM is now 10Mb since installing the new 8Mb RAM upgrade card with RTC by Amigakit, there's a real time clock which has been set to the correct date and time, but a few times recently it forgot the date and time, falling back to the default date of 01-01-1978. It has a UK keyboard, a Gotek drive is fitted and the power is on but currently has no USB stick inserted. I'm surrently in the middle of a game of Civilization. The game has disabled any details from appearing on my Workbench screen, although there is still a screen behind it with a bar saying "Workbench Screen", but apart from that it's just grey and blank. I'll post some details of my startup-sequence and other settings later. My WHDload version number starts with 18. This CF card came preinstalled with thousands of games and demos, but I don't think I could ever have installed that many bytmyself. I created a WHDload CF card by myself a few years ago, but only installed less than 30 games. I may not have tried to run more than 10% of the games on this card so far, but I'm just guessing.
This problem has made me think about what kind of replacement keyboard I could get if necessary. Unless I bought another classic A1200 keyboard by Commodore or ESCOM, then it may have to be a USB keyboard with an adaptor, as available on eBay. I found an Amiga A4000 keyboard for auction on eBay, but soon discovered it has a PS/2 type connector, although the keyboard itself isn't PS/2 because it produces different key codes, meaning that a translator is needed for anyone who wants to plug in a PS/2 keyboard to an Amiga A4000. In that case, any PS/2 adaptors designed for Amigas would have this translator built in, so they wouldn't be compatible with an Amiga A4000 keyboard. I don't know how I could make a keyboard by myself, so in that case, my most likely replacement keyboard would probably be an Apple Mac USB keyboard with Amiga stickers and an Amiga USB adaptor.