It's pretty common for weight to fluctuate a bit due to water retention etc. but it's not uncommon to put on some extra weight initially when you increase your training volume as often your appetite will increase. I wouldn't worry about it.
dont worry about it steve,ive just been on the nhs website and my bmi is 25.74 according to them im over weight!!!!!
I just read this thread title quickly and thought it said"Strength training has made me hairier, maybe".....There might be more in this alternative thread title, and Wayne Rooney might be interested too...
As long as you know the weight gain is reversible I'd take advantage of it. Your increased mass will provide a greater stimulus to your muscles making them stronger more quickly. Once you're done, lose it and crush.