Issue panning - I can't.

I've been using Reaper (on Mac) for about a year now and it's been great up until recently. I've had an issue surface within the last month that I have not been able to resolve no matter how much digging and researching I do. I've been using Reaper 32 bit and all of a sudden I can't pan tracks. I've tried adjusting the pan laws to no avail. My master is on mono and there are no plugins running on it. It doesn't matter if it's a new project or an old one (that used to pan no problem), no tracks will pan anymore. Most of the time when I pan all the way left, the track gets louder but stays in the center. Panning all the way right, the volume decreases until there's no volume at 100%R. I've tried all the solutions offered in other threads but they haven't made a difference. I have troubleshooted my monitors to make sure they aren't the problem. They aren't. I've recorded a couple tracks in Garageband to see if I can pan and I can, so it's not my interface. I downloaded Reaper 64 this morning. Viola, I can pan! My problem now, however is that my purchased plugins don't work in this version so unless I can figure this out I'm left with either using 32 and can't pan (ie: can't do anything other than track because mixing isn't an option this way) or 64 and plugins.

Can't pan. 

Sorry, I should have said that my options are 32 bit version WITH plugins but can't pan or 64 bit version, CAN pan but don't have purchased plugins.

I put master to stereo but that doesn't change anything. I've tried all variations, solutions. It's driving me batty...:)(

Is this specific to a certain project or affects all projects?

Thanks for the welcome! The problem is now with all projects - including ones that were working fine initially. As mentioned, I can use other DAWs, including Reaper 64 (I've been using 32) without a problem. I'd go to 64 because panning is working fine with it, but my purchased plugins don't in 64... Driving me crazy! : ( Thanks to all your help!

Have you tried re-installing 32 bit Reaper? Make sure to backup your Reaper configuration before uninstalling, but don't import your configuration right away in the new installation or you may import whatever setting has been inadvertently screwed up. Alternatively, it may be possible to import the configuration from the working 64 bit installation. Still, I'd back up my 32 bit config just in case. Depending on how much you've changed in the settings you may not even need a backup at all, but it is always prudent to do so just in case. The directions for backup/import of Reaper Config is in the manual.

have you tried uninstalling and reinstalling 32 bit reaper?

I have uninstalled and reinstalled. Nothing has changed.

I would you to go into the routing window of the Master. Are you 100% sure, that the master is not panned left and the Width is 100%? Vinod