The Interference theory refers to the idea that forgetting occurs because the recall of certain items interferes with the recall of other items. (In nature, the interfering items are said to originate from an overstimulating environment.) Within this context, Release from proactive interference refers to a situation in which conditions occur that eliminate or reduce the decrease in performance caused by proactive interference (Goldstein, 2008).
When an individual learns particular types of information, there is the possibility that previously learnt information will impair their learning of this new information. An example of this is learning a revised cell phone number. You may have the original number "imprinted" in your mind, so that with little trouble you can recall it. Imagine then that some digit in the number is changed, so that the number is similar, but different. Because you have the original representation of the number stored, when you recall the newly revised number, there is a good chance that you will accidentally recall the original number. This is an example of proactive interference (link to the article). Release from proactive experience occurs when the similar previously learnt information no longer interferes with the learning of new information, typically brought on by some change of conditions, such as changing the category (and thus, the meaning) imposed upon the information.
Was seen in the study by Wickens, Dalezman, & Eggemeier (1976) concerning semantic memory, where it was found that performance of recalling the names of stimuli improved when they were not related to previously learnt stimuli (in this case, professions, fruits, or meats).