The calculations the splitter performs depend a lot on the used configurations and scenario and thus it is not recommended to set styles related to padding, margin, border, etc the way have done this (it is OK to set colors, fonts, etc in this manner since they cannot affect the control's caluclations). With the code you have provided the issue you report is not reproduced - please accept my apologies for not mentioning this - I thought that in your original configuration you have additional settings which influence this and thus I thought that providing the correct way to style the content of the pane will be the fastest way to help you solve the problem and also to avoid further problems.
I prepared and attached a sample video capture of the tests of your code - I tested not only under FF but also under IE, with v 2009.3.1314.35 as you have noted and I also resized the browser (since no error was thrown on initial load) but to no avail - I could not get the js error you report. In case you want to further research this, please prepare and send code which is fully runnable and reproduces the issue along with very detailed reproduction steps. If the provided solution with a DIV also does not work for you you can provide more details why and we will think for the best advice we can provide for your specific case.
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