Hi tracy.moore, See if jscher2000's response to this question can help -

In the process of updating got a weird error message and Firefox won't restart https://support.mozilla.org/en-US/questions/1380185

this new update is terrible everything you try to open lags for ever !!!!!! slower then a snail going backwards seems the dev's really pushing users now to go to a other browser ... it has the same crappy slowness as that Google Chrome browser (1 of reasons i do not use chrome!!!) now it seems Firefox even more integrated the crap from there... ... give people when there is a update the easy reverse in case it it gives problems!!!! other hand will lose more users and the references will go from not to good anymore to bloody bad!!!!

An error message about XPCOM missing or about platform version usually happens because of a failed Firefox update that left you with a mixture of old and updated files in the Firefox program folder. This can happen in case security software was keeping a handle of some of the files in the Firefox program folder preventing Firefox from replacing all the files. You need to do a clean reinstall and remove the Firefox program folder to ensure that all files are replaced. You may have to disable security software temporarily in case the problem persists.

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release