Is there something wrong in the qt wallet setting or something wrong in source code?
Thanks for the help in advance
Were you able to transfer smaller amounts? Is this question related to your spending premine coins question?
I am not really sure of litecoin source code, but they do seem to be a clone of bitcoin as well. Going by that, if you have coins mined from genesis block you wouldn't be able to spend them as it was intentionally added by satoshi in main.cpp code. It's been some time I have stopped using bitcoin core but AFAIK the issue doesn't seem to do anything with your qt wallet.
If you are trying to spend a genesis block coinbase transaction, you can't do that and you need to change the source code as I have mentioned in your premine topic.