Sounds like an intermittenly sticking caliper or bad break line. When the flexable rubber breaks lines get old they can collapse and cause intermitten brake lockups. Also, bleeding the brakes may help out. Just remember that when you bleed the brakes you MUST bleed the entire system (all four wheels) in the proper order.
Also, your avatar is rather large and makes it hard to read the topics you've posted in :wink:
-Nick

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