I'm assuming you're growing the "European Blueberry" or "Bilberry" (Vaccinium myrtillus), rather than one of the North American blueberries like Highbush blueberry (Vaccinium corymbosum). The "European Blueberry" grows wild in Scotland, Wales, Ireland, England, Alpine countries, Poland, and northern parts of Russia. So I assume it likes cool temperatures! It may just be too hot for it in Greece right now. The American Highbush blueberry likes swamps and bogs, so I don't think you're overwatering, unless the "European Blueberry" is vastly different than the American one. The U.S.A. blueberry is also frequently found in shade in the wild, so you may want to be sure yours is not getting full Mediterranean sun. I would see if you can move it to a cooler spot. If you test the soil and it's too alkaline, you can acidify the soil with any type of plant food made for hollies and that sort of shrub, but I'm not sure what this type product would be called in Greece. Here we use something called "Holly-tone". Hope this helps...

To Eric and Fruitnut: Thanks for your kind replies. Here are the answers: ericwi: My water is from the rain barrel which collects the runoff from my roof. I've even put in 1/4 cup of white vinegar per gallon of this water to make sure it is acid enough. Fruitnut: the only fertilizing I've done is with "mir-acid" ( for acid loving plants rhodedendrons, azaelia, holly, etc ) at dillution of 1/2 the pkg reccomendation - which amounts to 1/2 tablespoon per gallon of water. I use this on the foilage and into the soil as well. The plants are from Miller's - last year I lost 5 of them, the Atlantic being the sole survivor which wintered over. Miller replaced them for me but my prospects for these look doubtful too. I'm normally pretty good at keeping plants going but these are proving a most frustrating challenge.

Do not mistake the normal wilting action caused by extreme cold as an indication of a problem. It is normal and will go away when milder temperatures return. In fact I would be much more worried if the leaves didn't curl up. Curled green leaves are a sign of a healthy azalea plant on cold days in winter. If we have an unusual spring drought, don't hesitate to water. However, spring droughts are very unusual. In general it is better to keep azaleas on the slightly dry side and never on the wet side. Good drainage is essential for healthy azaleas. Here is a link that might be useful: Henning's Rhododendron & Azalea Pages

I'm not hugely experienced, but that sounds like WAY too much water for a new plant. Also, unless you water is very alkali, acid every time you water is too much as well. Most local hardware stores have soil testers. I would recommend testing the pH of your soil and go from there as far as acidity. I'd also cut back to about 1/4 gallon a day at most unless its consistently over 90 and low humidity. The top of the soil can be a little dry in-between.