Here's the quote from the wiki article:
The main Western Christian source, Odo of Deuil, and Syriac Christian sources claim that the Byzantine emperor Manuel I Comnenus secretly hindered the crusaders' progress, particularly in Anatolia where he is alleged to have deliberately ordered Turks to attack them.
Is there any truth to this?
Not really. It certainly seems that Manuel I was not particularly inclined to help the Crusaders and didn't go out of his way to make things easier for them but actually going so far as to ally himself with the Turks would be too far. It's worth remembering that the Crusaders didn't exactly make themselves out to be great friends of the Byzantines in the First Crusade, they were supposed to hand Antioch over to Alexius I but didn't. We could argue whether or not they acted fairly but it's pretty clear the Byzantines felt that they were in the right on that issue. The First Crusade had done little to benefit Byzantium and wasn't without its problems (Crusaders raided parts of Byzantine territory on their march over) so the premise of a Second Crusade wasn't exactly what Manuel I wanted marching through his territory. Manuel's rather cold reception of the Crusaders, especially in contrast to Alexius' reasonably warm reception ~50 years earlier, didn't exactly endear the two parties. Add to that the fact that Manuel offered minimal assistance to the campaign and you can see why the Western Europeans didn't really like him.
Another major factor to consider for the Second Crusade is the fact that it failed. The First Crusade was such a resounding success that it was quite the embarrassment when the second failed. For one thing the Crusade was meant to be a mission endorsed by God. For another, the First Crusade featured no royals whatsoever on it while the Second had two (Louis VII and Conrad III). You would expect the presence of two of the most powerful kings in Europe to guarantee a success.
This left chroniclers of the Crusade in a very awkward position, they had to record a failure which is never ideal. It's interesting to note that the Second Crusade has nowhere near the same number of sources describing what happened as the First or the Third did. Odo of Deuil, the source in question, was in a particularly awkward position. He was sent on Crusade to write an account of how Louis VII acted heroically and defeated the Muslims in defense of his Christian brothers. That's not really what happened so Odo had to find someone to blame for his king's divine mission failing. He couldn't exactly blame Louis and it would be somewhat poor form to try and dump it on Conrad III. Instead he chose the Byzantines as the source of the Crusades failure and blamed much of the problems with the campaign on the treachery of the Greeks. There may have been some already existing animosity towards the Byzantines (mentioned a bit above) that helped push him in that direction.
Thomas Asbridge's The Crusades is a great general source on all of this. Jonathan Riley-Smith's The Crusades a Short History is also good but as you can tell from the title not quite as detailed.