Ah! so no replies from "humans"! I understand. Well, you really will need to wait until you hear from support staff unless you want to do some digging yourself. If you are sure that you have not come anywhere near your overall disk storage quota, it may be one of two other conditions that come immediately to mind:
1) Your user may have a quota set for its use that is only a small portion of your overall disk quota. This is common if you are one of many users on an account that is owned by another, or if you set a quota for yourself (your user) in the account control panel.
2) You may be having an issue with the number of files you have, rather than the amount of space you are using. This has to do with inodes, and there are limits to these in addition to your overall disk usage quota.
Here is how you can do a little research yourself to see what is going on while you wait for support to contact you:
Note that if you suspect it might be a "number of files" issue, then you will need to log into the shell to check that yourself.
--DreamHost Tech Support