Hello,
I have tried to reproduce this problem in a number of local test scenarios, unfortunately without much success. The error you are getting is an IE specific error, caused by slow/cyclic javascript/DOM manipulations by controls on page and could indeed be related to WebSplitter, but most probably a lot of factors play role in this, for example your GridViews size, other 3rd part control on page, etc.
I believe the fastest way to proceed in this situation is to contact our dedicated Developer Support department directly, if possible, with a small subset of your project reproducing the issue (if we have a repro, it will be much easier to figure out what is going on). Developer Support can be reached at:
http://www.infragistics.com/gethelp/default.aspx