I was using ANT Migration tool to deploy the components(e.g. Layouts, classes etc) from my machine to Sandbox last week. But, for some reason, though I have given the correct user name and password in build.properties file, it was giving me authentication error(Invalid username, password, security token; or user locked out).  I tried the same user name and password to log into Salesforce Sandbox using browser, I could login into it successfully. This looked very strange to me and then I found out the issue:

my password had two $ signs and for some reason, ANT was not able to recognise them. After, I changed the password by excluding the $ signs, it worked.

I thought of sharing this as it would help someone who face this issue since I had to spend about an hour to figure out the issue.