Why can't I break some blocks in creative mode?

I used to have a similar problem with lag due to the RAM being capped at 2GB for minecraft, and a game like that really needs more, however there is a way around this. Open up a notepad and copy the following text into it.

javaw -Xmx8192m -Xms4096m -jar "C:UsersYourUsernameDesktopminecraft.exe"

Just make sure that you have the exe for minecraft on your desktop and substitute YourUsername for the username on your computer. This above allocates 8GB of RAM for minecraft, its a good rule of thumb to not go above half of what you have. I have 16 so I went 8. If you have anything lower you can use the following numbers in place of the numbers in front of the Xmx.

3GB: 3072
4GB: 4096
6GB: 6144

so for example if you were allocating 3 GB of RAM you would put the following into notepad.

javaw -Xmx3072m -Xms3072m -jar "C:UsersYourUsernameDesktopminecraft.exe"

After you have the correct text inside of notepad all you have to do is save it as a BAT file. To do this just save as and then where it says Save as type, change it to All Files. Then in file name type in something like, MinecraftStartRAM.bat and save the file. Finally all you have to do is double click on the BAT file you just saved and it will run minecraft for you allocating more RAM than what it is manually capped at.

Hopefully this solves your problem, but if not there are other ways to increase RAM that I will post links to below. If what I link below fails I would just try to reinstall.

http://www.wikihow.com/Allocate-More-RAM-to-Minecraft

It is because the game is lagging.

It is more suitable to download Minecraft PE on Windows 10. You can download it from the App Store. If you download Minecraft PC, it will lag very badly.

There is 2 explanations.

1. You have a sword in your hand.
2. You've reached bedrock.

My explanations are 3:

1. You cant break stuff in creative while holding a sword
2. It might be a problem because of the java: It might malfunction or what, so i reccomend you reinstalling Minecraft
3. It might be a problem with your computer: When it is old, it has less than 2 MB of RAM (wich probably isnt it), its processor might be old and theese stuff.

I porbably didnt help you.

There probably are some invisible entities, as that'd only affect some blocks (which they stand on or next to) and spamclicking will eventually make you go around it. Check in spectator mode (/gamemode 3) and then find the source (which probably are command blocks)

Sometimes all you need to do is go to Settings, Keyboard and Mouse, then scroll down and reset these to default settings. It worked for me!