Try setting PostgreSQL to ignore damaged data by clicking Start --> Programs --> PostgreSQL --> Configuration Files --> Edit postgresql.conf. In the configuration file that appears, go to the bottom of the file and add the text "zero_damaged_pages = on" on a new line and then save and close the file. Click Start --> Programs --> PostgreSQL --> Reload Configuration and PostgreSQL will ignore the damaged data and might resolve this issue for you.
You can reindex your database from the PostgreSQL command prompt. Click Start --> Programs --> PostgreSQL --> psql to template 1. At the prompt that appears, type "reindexdb -a" and hit enter. Be aware that if you have large databases this may take a while, so be patient and wait for it to finish.
Try using the Command Prompt instead of psql to postgres; reindexdb is a program in the PostgreSQL directory, not a postgres command, and I should've suggested the command prompt . . . sorry about that