IBM shares dropped $4, or 3 percent, to $125.50 in morning trading.
In the past three months, the value of the euro has fallen nearly 10 percent, from 95 cents to 86 cents. "That's a pretty significant change in that short a period of time," Conigliaro said.
In a research note, Conigliaro reduced her revenue growth rate for IBM to 6.6 percent in the third quarter, down from 8.4 percent, and to 9.4 percent in the fourth quarter, down from 13.9 percent.
She also reduced her earnings-per-share estimate for the company by 3 cents, to $1.50 a share in the fourth quarter. For the year, Conigliaro said she expects IBM to earn $4.45 a share, down from an earlier estimate of $4.50.
"The currency situation, particularly the euro, has gotten considerably worse over the last couple of weeks," Conigliaro said. "IBM has big international exposure, and unlike some of the other, faster-growing companies that can moderate this kind of an impact, IBM is a larger, slower-growing company."
At the same time that she downgraded revenue estimates, Conigliaro maintained bullish growth prospects for the company. Excluding the negative effects of the currency decline, Conigliaro raised her growth estimate for the third quarter to 10.3 percent, up from 9.7 percent.
"The irony is that at the same time that we lowered our reported numbers for Q3 and Q4, we also think that the fundamental picture is not only improving but has the possibility of being slightly better, if you don't count currency," she said.
Conigliaro forecasts strong growth for IBM in Unix servers, disk storage and semiconductors.