Maybe something has been updated on your Macs recently (like Java or something related)? Not sure where Spark profile is on OS X, but on linux it's at /home/user/.Spark (hidden folder). You can try renaming it to something else, the nstart spark and let it create a new profile. Check if that solves the issue.
Other than that i can only suggest to try the latest build of Spark, but for Mac it is in the form of an archive, not an installer http://bamboo.igniterealtime.org/browse/SPARK-NIGHTLYMAC-288/artifact/JOB1/Spark /Spark.tar.gz