Hi Jennifer, thanks for your effort trying to repro this behavior. It's great to see this level of support on the forum, from you and the Corel team!
I too am experiencing the issue as described above, while running Snow Leopard 6.1 with your latest patch. For me, I start Painter Essentials, select "Start Drawing & Painting" from the initial dialog box at start-up. Once running, the brush drawer works fine until I switch to another application (E.g., Safari, check Mail). When switch back to Painter Essentials, the brush drawer is no longer visible (similar to the pre-patch issue with Snow Leopard). As noted above, then switching to the Photo Painting tab, then selecting the "Brush" button in the Auto-Painting drop down, then going back to the Drawing & Painting tab, brings back the brush drawer. Please let me know if there is anything further you would like tried or additional info that would help, to better understand this issue.