Guys, I think I found a solution on Win 7. 
 
 - Right click on corsairs.exe and select "Properties"; 
 - Select the "Compatibility" tab; 
 - Check the "Disable desktop composition" option; (it will disable windows aero while the application is running) 
 - Apply and confirm, then start the game. 
 
 After all this my game runs like a charm: no lags inside the main menu, no lags while moving storage ship/ship or ship/city and, most important, no lags while boarding! 
 
 Unfortunately I noticed an increased instability, so crashes are more frequents but still, the game runs better than before, just spam "s" to quicksave and you're good to go! 
 
 I hope this will help you all: this is working for me, anyway, and I thought that this could be helpful to others having the same issue. 
 
 - Metalloman - 
 
 
 UPDATE: I found that Map1 in adventure mode (English campaign) is the only one to be bugged: going forward with the campaign, playing the other maps I had no bugs nor crashes.
Post edited February 21, 2016 by Metalloman