I've noticed this with the last 2 betas but the issue has been probably there since the beginning. Playing large balanced map, all 8 sovs with expert AIs, moderate monsters and epic speed. I can go on and play for 300 or 400 turns and pretty sure even more but after around turn 200 when the map is more than 50% revealed and I have lots of cities and other buildings on the map all the saves made seem to be corrupted in some way or even worse, trying to save the game will cause a CTD. I either have to play without 0 reloads or save attempts or from around turn 180 onwards be very careful and save every 3 turns, go back to main menu and load that save and press end turn. If it works go forward, if not and CTD then go back to the last good save 3 turns ago. This happens in absolutely every game I play.
It's also pretty easy to see whether a save is good or not as while loading a good save the load bar will fill up quickly even if it stays for around 5 seconds at the end before actually loading the map while with a bad save the load bar is usually stuck midway through loading for quite long (sometimes 10+ seconds). When a bad save is loaded sometimes information is missing from the UI (discovered factions disappear from the power rating list) or the ledger (relations report is empty).
My PC is pretty good (W7 Ultimate, I7, 6GB DDR3, 5800 1GB, 1TB WD Caviar Black 7200 rpm with over 100GB of free space, latest drivers on pretty much everything that counts for a video game). So it looks to me like it is not my PC but the game that has some memory leak or other issue that corrupts the saves from a point forward when there are a lot of revealed items, armies etc. . I have encountered other numerous strange bugs but this has actually been the only game breaking one for me. Hoping it gets fixed in beta 5 (a little worried we're so close to 1.00 and this issue is still present) as from my part I've helped with 2 posts signaling the issue with proper information attached from both 0.95 and 0.915.
One question for the beta community as a confirmation, do a lot of you guys have the same or similar issues?