files in guest shared folders seems not to reflect changes done in host

I have a guest OS (Ubuntu Hardy Heron) with shares a folder (in read/write) with the host OS (Ubuntu Hardy Heron). I use a web editor to edit the files in this folder in the host OS so the modifications should be seen in the guest OS (the shared folder, mounted in the guest, is the root directory of an apache web server installed just in the guest). The problem is that, when I modify a file in the host side, these changes seem not reflected correctly in guest side. Via a simple cat or less or vi the modified files seem correct but with apache the modifications aren't reflected (I can test this via "telnet server 80"). In fact often the modifications are seen as strange characters or other times other strange behaviours happen. I can solve this either:

• umount and then re-mount the shared folder (but I have to do this after every file change)

or

• simply edit the file via vi (guest side) and, with no modifications, save the file