Having the same issue here. What I've tried so far: 1. Downloading all the .jars manually and adding them to "fml\mcp_data\jars" as per Lex's advice here http://www.minecraftforge.net/forum/index.php?topic=11898.0 Re-running the installer simply reports the jars as modified, deletes them and then fails when trying to re-download them. 2. Setting up MCP independent of Forge, which does successfully download the libraries. Again then adding them to "fml\mcp_data" but Forge still regards them as modified, same as before. Is there anyway to stop Forge removing the libraries? As they definitely aren't modified.