There have been two others that have had the issue as well.

Shortly after training my first batch of spells, I found that everything began to resist everything I cast. It did not matter whether the mob was gray, green, yellow or orange, everything was resisted.

I've tried creating a different character (thus the mage), clearing the cache, resetting the level and resetting all of the spells in hopes of correcting it.

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After toying around with it, I found out by removing the Rockfury Bracers that I was wearing, I was able to cast again.

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Edit: Then again, that didn't work RIGHT after. Upon taking off Pam's Prom Dress and the Rockfury Bracers, however, I had no issue.