Without any additional information available, it sounds like your database (the archive.nsf file) may be corrupt. There are several good tools out there, some free, some not, which will address this issue:
http://www.download.com/Quick-Recovery-for-Lotus-Notes-Server-/3000-2248_4-10586494.html?tag=lst-4&cdlPid=10586495 (this is server-side only)
Try one of them – you should be OK (provided of course the file is actually corrupt…).
you can Try this software for your solution: http://www.recoverdatatools.com/notes-outlook-conversion.html