Welcome aboard mikechristine, understand that your SWF is like a separate element, it is not affected by browser. However, if you're seeing differences in how it's rendering, my guess would be that when embedded in IE, **something** is hogging up memory. It could be how IE renders Flash, the version of plugin you're using (upgrade it,) or more likely, your Flash is coded in such a way that it's not using memory efficiently.
Inefficient Flash is probably one of the largest reasons so many people hate Flash, or claim that it "crashes" their browser. It's too complex a topic to cover in a post, especially without knowing the environment, but some of the heavy hitters in Flash are:
- excess keyframes - overuse of transparencies and gradients - inefficient use of internal variables, that is, when a variable is created and populated, it takes space in memory. When done with this variable, it will continue to take up space in memory unless you unset/undefine it, which can lead to a progressive overuse of memory. This is especially true of dynamically created movie clip objects. - including objects directly in the movie that can be dynamically inserted externally as needed, for example, putting an entire video in the timeline instead of importing it on demand. - Using fonts and text directly in the Flash, rather than converting them to outline symbols. Sometimes it's impossible to get around this, as in imported text, but wherever you can, convert your text objects to outlines. - Simplify shapes wherever you can. - If you can do a mask in another way, do it, extensive masking can tax memory and performance.
There are many more ideas in the help files, search for "Optimizing Flash."