My chain appears to be squeaking when I ride it forward but not backwards At first I thought I just needed to lubricate my chain, so I degreased it and just re-lubed it very thoroughly.  It's still squeaking.  I thought it could maybe be a derailleur pulley issue, but I noticed that the squeak only occurs when the chain is pulled forward and not when it freewheels backwards.  Is there any condition that would cause a chain/pulley/whatever to squeak in only a single direction?

I understand that torque load can sometimes be a factor, so I tested it by pedaling with minimal (near-zero) force and it still squeaks in only the forward direction, so it doesn't seem to be affected by heavy load vs. light load.

The only change I have made recently was that I took out and regreased my derailleur pulleys, but they were fine for about a week until today when it was lightly raining in the morning.  It seems plausible that the rain somehow messed up my pulley greasing, but I don't understand why it would be a unidirectional problem.

Thank you to anyone who gives me suggestions or ideas or whatever.
Since you have 3000 miles on the current chain, it is quite possible that you are nearing the end of the life span of the chain.  An easy way to check this is to grab a ruler and measure 12 links. Remember that a full link has both an inner and outer section so a full link will look something like this : (0)=(0)=()
So count every other pivot.  Each link should be ~1 inch.  12 links should = 12 inches.  If 12 links on your chain is more than 12 1/4 inches you should replace the chain.  This would be a good time to check the rest of your drive train for wear too.