There is the PVSW.log. Depending on your version of PSQL, you can find them in the following locations:
Prior to v10: C:\PVSW\BIN (assuming that PSQL is installed on the C:\ Drive).
v10: C:\Documents and Settings\All Users\Application Data\Pervasive Software\PSQL\Logs
NOTE: For the v10 location you may need to change the Folder Options in Windows Explorer to show hidden files and folders.
You can also look in the OS Event Logs. Right-Click on My Computer, select Manage. Under Event Viewer, look at Application and System. You may see an event for PSQL captured there.