"Yes, some strange goings on. I heard that the then Russian President (Yeltsin) agreed to their independence after a 'bender' and that the Ruskies have regretted it ever since. "
Er, I think you heard wrong (!) Crimea was transferred to the Ukraine SSR by Krushchev in the 50s. It was initially annexed to the Russian Empire by Catherine the Great. It is a complex area ethnically. Sevastopol is a very Russian city, but there are many Ukrainians, and Muslim Tatars also. And a sizeable number of Greeks, Greece having a historical ties to the region (hence the Greek names of places like Sevastopol, Simferopol, Feodosiya etc.)
I don't think Russia is "invading" Crimea as such. Putin is cross about losing his man in Kyiv, but mainly they are paranoid about the new government there trying to cancel the lease their Black Sea Fleet has in Sevastopol (also the home tot he Ukrainian Navy). If they lost that they'd lose a massive amount of military and hence diplomatic influence.
The danger is though, that as in Sarajevo 100 years ago, a spark in a powder keg triggers events that spiral out of control. My guess is that nowadays with quicker communications between leaders, that sort of thing is less likely. I hope I am right