Archives/SFX/Setups fail to open on shared folders *SOLVED*

[danf84]

I am having issues whereby application setup (exe archives) won't run, spitting out read errors. WinRAR also fails to extract from these Setup files; it also fails to extract from ISOs, RARs or CABs.

I only started noticing it after trying to upgrade my XP base image with nLite, so I could say end of June everything worked.
Here's an example of error from WinRAR "Read error in the file S:\Updates\WindowsXP-WindowsMedia-KB952069-v2-x86-ENU.cab" (when openning the file). Then "The Parameter is incorrect, Read Error in the file".

If I copy the file into C:\ for example, it opens fine.
nLite won't work at all with them; giving me similar errors.

Is there a file open mode of some sort that Shared Folders in VirtualBox has disabled/broken?

I am using the latest release (4.1.2), but the previous one has the same problem.

Regards, Dan

EDIT: I updated Guest Additions and the problem went away