Removed good response... you posted the same question on the thread you have about saving heating/cooling cost.

Doh!

I used to be able to open them, but had cats so I rarely did. It was only after the outside of the house was painted that I couldn't get them to open, so I'm 90% sure that the outside paint is the issue.

Honestly, I wouldn't be AT ALL surprised to find out that the painter opened the windows, painted inside the frame, and then shut them. That's just how my luck goes... LOL

I'm not afraid of ladders or heights at all, just pointing out that I'm limited when it comes to getting tools up there :-) I'll climb up with a putty knife this evening, when it's cooler and wasps have chilled out.

Try using a sash saw like this. They have very thin blades and are purpose-made for this job.

Or a vibrating tool has a thin enough blade to cut through the paint without damaging the sash and frame.