Hi Gareth,
It is problem related to excel versions, I hope you have higher version (2010) and user might be having lower version OR opening your saved view in 3.x explorer.
- If they are using lower version, then obvious ask them to upgrade it OR you use the same version as users.
- If they are opening your saved view in 3.x explorer, then correct them.
- If both of above are not true, then allow macros in users Excel. I mean, goto options and in security section, there is a option to allow/enable all macros (security level LOW). choose that it should solve your issue.
Let me know the versions of excel, I'll guide you to find the option if you need.
Note: I have faced the same issue, while user opening 7.x report in 3.x explorer.
Update us once the issue is solved, your solution will help others.
Thanks,
Umashankar