Which frame are you trying to hide ? It may not necessarily be a fault with another addon, but default UI code, can under certain circumstances do this.
If said frame is being shown by another addon, after hiding it, you probably need to hook its Show method, in addition to hiding it. For example:
Code:
hooksecurefunc(<FrameName>, "Show", <YourFunctionName>)
Note that hooking however should be used wisely, since conflicts are also likely to occur, in cases one or more addons are hooking the same function or method. In that particular case, your only hope is to use a hooking library as long as the "offending" addon is also using it.