Do you have Windows 7 SP1, and Photoshop CS5 ME edition?
I ask because there's been another problem just noted on this forum with Hebrew text being backwards under the above conditions: http://forums.adobe.com/thread/795994?tstart=0
The workaround for that user seemed to be to edit some text that's in the proper order and complete the edit. Perhaps this set up something in the CHARACTER panel that allows the text to then flow in the proper direction for further text operations.
You could also try making the CHARACTER panel visible and choosing Reset Character from the fly out menu, available from the little icon at the upper-right.
There is a Middle Eastern version of Photoshop that has support for ight-to-left languages, available from WinSoft. Cost is similar (more, actually) to the US version, but if you do this a lot, it may be worth the investment.
There are special, "Mirror Image" fonts available for Hebrew and Arabic. After pasting into Photoshop, Edit > Transform > Flip Horizontal.
There is a Reverse Text Generator on-line at http://textmechanic.com/Reverse-Text-Generator.html. Paste your text into the box, reverse it, and copy and paste to Photoshop. This method does not seem to work properly with Arabic, though.
Hello there. I may be late in replying, but I just experienced the challenge of trying to get Hebrew to read correctly in Photoshop and Illustrator. Well, reading and screwing around for hours, I have a solution that is SO simple. I couldn't believe it. In both programs, just adjust the Kern in the Character window of either program to a negative number. I had to set mine to -880 and it worked! Check out my screenshots below for before and after: