Please can you answer some questions so we can help.
1. Does your PSP start up ok? (Can you see this?
Google Image Result for http://upload.wikimedia.org/wikipedia/en/7/7a/XMBPSP.jpg )
2. Have you recently upgraded the firmware?
3. Have you been in to the recovery menu recently?
4. If answer to Q1 is yes, then try to upgrade your PSP to the latest firmware.