Strange error message on first login with IE6

[lawe]

Hi,

I hope I chose the right sub-forum.

Our users have a strange problem when they are trying to log into the web-interface of our zcs-5.0.16-OSE with InternetExplorer6. On their first attempt they always get the following error message:



Which translates as follows:

Line: 30059
Character: 3
Error: 'ZmErrorDialog' is undefined
Code: 0

and the login gets stuck like shown in the following linked picture: click me. As soon as they try to login again, it succeeds so this is not a showstopper but anyway quite annoying.
Unfortunately we cannot force those users to upgrade their InternetExplorer to any newer version due to the rules of their company.

Do you have any idea or suggestion how we could get rid of that problem?

Kind regards
LaWe