I just lost nearly 2 million credits as well.
I had 120 palladium, which I bought for 12,000 and the sale price was 14999. I didn't check how much money I had after selling, but it obviously should have sold for over 1.6 million credits. I then went to fill my hold with computer components, but the market returned an error and I didn't receive the cargo. However, my credits were now down to 500,000. So either I got screwed over selling the Palladium, or the error took my credits.
Either way, it's basically an hour's play session gone.