Hi,
Welcome to Ext.NET!
It should not depend on server. It depends on browser.
I was able to reproduce the issue in IE9 with IE7 and compatibility modes.
Please note that any IE compatibility modes are not officially supported. Please ensure it's switched off.
Here is some info how to avoid the compatibility mode.
http://forums.ext.net/showthread.php...ll=1#post86658
The issue may be also reproducible in the original IE7 (maybe, IE8 as well). If yes, please put the field into an additional container with FormLayout. Generally, using a FieldLabel within a container with FormLayout gives more consistent result across all browsers (it is mainly related to IE < IE9).