cannot open word/excel documents

[cabybood]

i've run into the issue where i cannot open certian word or excel documents when another person on my network has the file open. Usually, i get an option to access the file as "Read-only" but on certain files (and i cannot find a commonality between them), it simply says the the file could not be found and to check the spelling. I am using office 2007, but only recently upgraded and had the same issue with office 2003. Any ideas on how to fix this?