When trying to enter level 120 of the mines, the game crashes. This has happened both times that I've tried it.

I have the same thing on level 110 of the mines.

Three times. Happens on full screen or windowed.

Other people recommend having space in your pack which i have tried still no luck.

Edit:

Looks like other people are having issues with it as well. the game is trying to connect to steam for an achievement.

Message: Could not load file or assembly 'Steamworks.NET, Version=7.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.
InnerException:
Stack Trace: at StardewValley.SteamHelper.getAchievement(String achieve)
at StardewValley.Game1.getSteamAchievement(String which) in C:\Users\Barone_\Documents\Visual Studio 2010\Projects\Farmer\Farmer\Farmer\Game1.cs:line 5398
at StardewValley.Locations.MineShaft.addLevelUnique(Boolean firstTime) in C:\Users\Barone_\Documents\Visual Studio 2010\Projects\Farmer\Farmer\Farmer\Locations\MineShaft.cs:line 1129
at StardewValley.Locations.MineShaft.populateLevel() in C:\Users\Barone_\Documents\Visual Studio 2010\Projects\Farmer\Farmer\Farmer\Locations\MineShaft.cs:line 666
at StardewValley.Locations.MineShaft.enterMine(Farmer who, Int32 mineLevel, Boolean ridingElevator) in C:\Users\Barone_\Documents\Visual Studio 2010\Projects\Farmer\Farmer\Farmer\Locations\MineShaft.cs:line 179
at StardewValley.Game1.UpdateOther(GameTime time) in C:\Users\Barone_\Documents\Visual Studio 2010\Projects\Farmer\Farmer\Farmer\Game1.cs:line 2709
at StardewValley.Game1.Update(GameTime gameTime) in C:\Users\Barone_\Documents\Visual Studio 2010\Projects\Farmer\Farmer\Farmer\Game1.cs:line 1455
at Microsoft.Xna.Framework.Game.Tick()
at Microsoft.Xna.Framework.Game.HostIdle(Object sender, EventArgs e)
at Microsoft.Xna.Framework.GameHost.OnIdle()
at Microsoft.Xna.Framework.WindowsGameHost.RunOneFrame()
at Microsoft.Xna.Framework.WindowsGameHost.ApplicationIdle(Object sender, EventArgs e)
at System.Windows.Forms.Application.ThreadContext.System.Windows.Forms.UnsafeNativeMethods.IMsoComponent.FDoIdle( Int32 grfidlef)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManage r.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(Form mainForm)
at Microsoft.Xna.Framework.WindowsGameHost.Run()
at Microsoft.Xna.Framework.Game.RunGame(Boolean useBlockingRun)
at StardewValley.Program.Main(String[] args) in C:\Users\Barone_\Documents\Visual Studio 2010\Projects\Farmer\Farmer\Farmer\Program.cs:line 31


Edit 2:

Logged into Steam still failing.

This is a known bug that has been fixed with the latest patch. The patch however have not as of this post yet been released. It should arrive today some time however, if everything goes smooth.
Stardew Valley has been 3 patches behind already because of patches not being delivered during weekends, fault of GOG.

Updated the game with today's patch and now everything is working properly!

I can also confirm that the latest patch (redownload the GOG.com file) fixes this issue.