The error prompt is "Lightroom encountered an error when reading from its preview cache and needs to quit." In small subtexts it states "Lightroom will attempt to fix this problem the next time it launches"
Lightroom has yet to fix the problem and I do not have access to my lightroom catalog.
Rename your Preview Cache. It is in the same location and has the same name as your Lightroom Catalog. Rename it to catalogname.lrpreviewold and when Lightroom launches, it will rebuild the Preview Cache.
Does this allow you to open your catalog?