A couple years ago, we had large pastes causing a QlikView export to Excel to choke.
We discovered that if the end user already had another instance(s) of Excel running when using the CopyTableToClipBoard function, Excel didn't do its normal initialization and would not flush the Office 24page Clipboard. (Which is separate from the single page System clipboard.) So large pastes would choke if the Office Clipboard was already populated data from earlier copy/paste operations.
We also found that the vb command to clear the Office Clipboard was not reliable nor was the workaround of pushing 24 single cell clips.
We fell back to requiring users to close Excel before exporting.
Perhaps there is a better way?