I have had the same issue, though nowhere near as bad as you.
In IE browser, it would often take a second or two between performing actions, like entering text, clicking on buttons etc.
Recently, I had to change the Web Object tree model in TestComplete from TAG to TREE. This has improved performance in IE browser significantly.
Funny thing is that I never had any performance issues in Firefox.
Depending on how many tests you have already, and what model you use, it might be an idea to change it. Even though i currently have only a few scripts, it has still been a major rewrite of almost all my generic code to use the new object tree model.
