Seemingly Plugin Conflict

Strange effects: Purchased, downloaded & activated Slider Pro, uploaded photos, but no images appeared. Continuous reload spin but no images; “error” msg received in upper left corner of Firefox, Flock, & G Chrome. Safari ok. Attempted to find problem by deactivating & reactivating plugins, but now this returns a 404 error msg. Those deleted plugins still show activated. Also, widgets are ‘frozen’ & cannot be repositioned. Strangely, text widgets and some others have disappeared and no longer show on my site, suffering loss of information. Contacted developer who tried to assist, but has no idea why Slider Pro does not work. Contacted BlueHost for support, and they suggested that it was a conflict between plugins, but could not further identify cause. They were able to deactivate the Slider Pro plugin, and suggested contacting WordPress. The problem as since spread and now causes sign in problems where site opening page is meshed with admin sign in page in the browser. Never experienced this before. All browsers are update current, as well as WordPress (both site and host). I’m using MacBook Pro with current Apple update for Snow Leopard. I’m three days into this problem that seems to be getting worst, so, I’ve stop all efforts to make corrections until I hear back from you guys.