If you are getting an access violation then you will likely find errors like these in the HWRM log:

LUA 'data:UI\subtitle.lua' -- parameter: invalid control char;
last token read: `0x10' at line 1 in string ""
Can't load subtitle config file!
LUA 'DATA:\UI\NewUI\Main\Background.lua' -- parameter: `=' expected;
last token read: `?' at line 1 in string ""
LUA 'DATA:\UI\NewUI\Main\NewMainMenu.lua' -- parameter: `=' expected;
last token read: `?' at line 1 in string ""

Your HWRM.log file will be in your Steam directory and in the same folder that HomeworldRM.exe is in. The first part of the path changes depending on where you install Steam, but the tail end is as below:

*\SteamLibrary\steamapps\common\Homeworld\HomeworldRM\Bin\Release\HwRM.log

If this is the case then you have likely killed the HWRM launcher when it was unresponsive, this unresponsive time on load is when it is copying the mod files from the Steam download folder.

To fix this find STCR.big in your Steam folder (there should be 2 copies) and delete the copy under the Homeworld directory. Relaunch the HWRM launcher and leave it alone until it has finished the copy operation

You should then be ok to play!

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2025:

One new thing, might need to make the game "large address aware" in some cases
https://www.techpowerup.com/forums/threads/large-address-aware.112556/