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When openlp.org closes, it appears to close PowerPoint too, regardless of whether you had any PPT's open outside openlp.org.
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So a future feature request is for openlp.org to only 'close' the powerpoint presentations that it has opened itself. If there are still any presentations open (which in my case were some that were open before openlp.org was started), then don't exit PowerPoint, but leave it running.
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