I had this on a new hosting account. I repeatedly asked tech-support to fix the permissions. Strange thing was this site had both asp and asp.net pages. The asp pages updated their database ok but the asp.net pages always gave this error (seperate access database files). I assumed they had forgoten to fix the permissions on one file. However I just happend to google the error and found the reference link that suggested adding

<identity impersonate="true" />

to the <system.web> node in web.config. Bingo, that did it.