Common causes for "corrupted data" when transferring iTunes videos to PSP:
PSP supports mainly MP4 (H.264) and AVI (Xvid). iTunes may encode differently. Check PSP manual/Sony site for supported formats.
PSP has max file size limits. Convert to smaller size or split files.
Even correct format may have incompatible settings (resolution, bitrate). Experiment in iTunes or use a converter.
Re-download or convert with different software.
Update PSP firmware to latest version.
If persistent, may be hardware issue—contact Sony Support.