I did have the same problem before. My account did have an infinity next to disk space usage but now it is limited to 1024mb.
according to their free account signup (http://www.x10hosting.com/free-hosting-signup) which the page is not available at the moment says all free account have unmetered harddisk space and bandwidth. I'm not sure what exactly happened to that.
There was a recent change to our disk space policy. If you meet to following criteria, you can request unlimited disk space
- Account must be one week old
- You must be using at least 50% of your storage space
- You must have a working website online that falls inline with our terms of service