At a quick glance i note:

On the delete statement:

1) sql = "DELETE FileInfo.[Comments] FROM FileInfo WHERE FileInfo.[FileName] = '" & selectedFile & "'"

2) Else just do this rst.fields("Comments") = ""

On the Update statement:

1) sql = "UPDATE FileInfo SET Comments = " & "rst.Fields("Comments").AppendChunk strdata " & "WHERE FileInfo.FileName =" & selectedFile

Just those "" could help!

Good luck!
b