FYI I have been tracking this problem down. I believe I have a handle on it and have made some adjustments.
Please PM me with details if you continue to have difficulty with the site.
The root of the issue appears to be with security software which protects the site from hackers and other bad actors, where legitimate posts are sometimes being triggered as a false positive.
I apologize for the inconvenience and we will work to resolve as quickly as possible.